Here is a partial list of images that are possible to override using the theme folder.
Images
Trayicon.ico
2XClientLarge.png
2XClientSmall.png
AmmyyAdminLarge.png
AmmyyAdminSmall.png
AnydeskLarge.png
AnydeskSmall.png
AnyplaceControlLarge.png
AnyplaceControlSmall.png
AwrcProLarge.png
AwrcProSmall.png
AxelViewerLarge.png
AxelViewerSmall.png
AzureStorageExplorerLarge.png
AzureStorageExplorerSmall.png
BarracudaNgFirewallLarge.png
BarracudaNgFirewallSmall.png
BitviseSshClientLarge.png
BitviseSshClientSmall.png
BomgarRepresentativeConsoleLarge.png
BomgarRepresentativeConsoleSmall.png
CiscoAsdmLarge.png
CiscoAsdmSmall.png
CitrixNetscalerLarge.png
CitrixNetscalerSmall.png
ContactCompanyLarge.png
ContactCompanySmall.png
ContactCustomerLarge.png
ContactCustomerSmall.png
ContactDefaultLarge.png
ContactDefaultSmall.png
ContactEmployeeLarge.png
ContactEmployeeSmall.png
ContactFamillyLarge.png
ContactFamillySmall.png
ContactSupplierLarge.png
ContactSupplierSmall.png
ContactSupportLarge.png
ContactSupportSmall.png
CredentialAppleKeychainLarge.png
CredentialAppleKeychainSmall.png
CredentialChromePasswordManagerLarge.png
CredentialChromePasswordManagerSmall.png
CredentialConnectionStringLarge.png
CredentialConnectionStringSmall.png
CredentialDefaultLarge.png
CredentialDefaultSmall.png
CredentialFirefoxPasswordManagerLarge.png
CredentialFirefoxPasswordManagerSmall.png
CredentialKeePassLarge.png
CredentialKeePassSmall.png
CredentialLastPassLarge.png
CredentialLastPassSmall.png
CredentialOnePasswordLarge.png
CredentialOnePasswordSmall.png
CredentialPMProLarge.png
CredentialPMProSmall.png
CredentialPasswordBoxLarge.png
CredentialPasswordBoxSmall.png
CredentialPasswordSafeLarge.png
CredentialPasswordSafeSmall.png
CredentialPasswordVaultManagerLarge.png
CredentialPasswordVaultManagerSmall.png
CredentialPasswordstateLarge.png
CredentialPasswordstateSmall.png
CredentialPleasantPasswordServerLarge.png
CredentialPleasantPasswordServerSmall.png
CredentialPrivateKeyLarge.png
CredentialPrivateKeySmall.png
CredentialSecretServerLarge.png
CredentialSecretServerSmall.png
CredentialWindowsVaultLarge.png
CredentialWindowsVaultsmall.png
DataEntryAlarmLarge.png
DataEntryAlarmSmall.png
DataEntryBankInfoLarge.png
DataEntryBankInfoSmall.png
DataEntryCredentialLarge.png
DataEntryCredentialSmall.png
DataEntryCreditCardLarge.png
DataEntryCreditCardSmall.png
DataEntryCustomLarge.png
DataEntryCustomSmall.png
DataEntryEmailAccountLarge.png
DataEntryEmailAccountSmall.png
DataEntryPassportLarge.png
DataEntryPassportSmall.png
DataEntrySafetyDepositLarge.png
DataEntrySafetyDepositSmall.png
DataEntrySecureNoteLarge.png
DataEntrySecureNoteSmall.png
DataEntrySerialLarge.png
DataEntrySerialSmall.png
DataEntryWalletLarge.png
DataEntryWalletSmall.png
DataEntryWebLarge.png
DataEntryWebSmall.png
Database.NetLarge.png
Database.NetSmall.png
DbVisualizerLarge.png
DbVisualizerSmall.png
DocumentCertificateLarge.png
DocumentCertificateSmall.png
DocumentDefaultLarge.png
DocumentDefaultSmall.png
DocumentExcelLarge.png
DocumentExcelSmall.png
DocumentImageLarge.png
DocumentImageSmall.png
DocumentOneNoteLarge.png
DocumentOneNoteSmall.png
DocumentPDFLarge.png
DocumentPDFSmall.png
DocumentPhoneBookLarge.png
DocumentPhoneBookSmall.png
DocumentPowerPointLarge.png
DocumentPowerPointSmall.png
DocumentTextLarge.png
DocumentTextSmall.png
DocumentVisioLarge.png
DocumentVisioSmall.png
DocumentWordLarge.png
DocumentWordSmall.png
EricomBlazeClientLarge.png
EricomBlazeClientSmall.png
FileExplorerLarge.png
FileExplorerSmall.png
FlashfxpLarge.png
FlashfxpSmall.png
GateprotectFirewallAdministrationClientLarge.png
GateprotectFirewallAdministrationClientSmall.png
GroupCompanyLarge.png
GroupCompanySmall.png
GroupCustomerLarge.png
GroupCustomerSmall.png
GroupDatabaseLarge.png
GroupDatabaseSmall.png
GroupDeviceLarge.png
GroupDeviceSmall.png
GroupDomainLarge.png
GroupDomainSmall.png
GroupFolderLarge.png
GroupFolderSmall.png
GroupIdentityLarge.png
GroupIdentitySmall.png
GroupPrinterLarge.png
GroupPrinterSmall.png
GroupRootLarge.png
GroupRootSmall.png
GroupServerLarge.png
GroupServerSmall.png
GroupSiteLarge.png
GroupSiteSmall.png
GroupSoftwareLarge.png
GroupSoftwareSmall.png
GroupWorkstationLarge.png
GroupWorkstationSmall.png
HeidisqlLarge.png
HeidisqlSmall.png
HpIntegratedLightsOutLarge.png
HpIntegratedLightsOutSmall.png
IbmPersonalCommunicationsLarge.png
IbmPersonalCommunicationsSmall.png
IslLightDeskLarge.png
IslLightDeskSmall.png
JavaWebStartLarge.png
JavaWebStartSmall.png
MacroScriptAppleScriptLarge.png
MacroScriptAppleScriptSmall.png
MacroScriptAutoHotKeyLarge.png
MacroScriptAutoHotKeySmall.png
MacroScriptAutoITLarge.png
MacroScriptAutoITSmall.png
MacroScriptCommandLineLarge.png
MacroScriptCommandLineSmall.png
MacroScriptDatabaseQueryLarge.png
MacroScriptDatabaseQuerySmall.png
MacroScriptJitBitLarge.png
MacroScriptJitBitSmall.png
MacroScriptMacroLarge.png
MacroScriptMacroSmall.png
MacroScriptPSExecLarge.png
MacroScriptPSExecSmall.png
MacroScriptPowerShellLarge.png
MacroScriptPowerShellLocalLarge.png
MacroScriptPowerShellLocalSmall.png
MacroScriptPowerShellSmall.png
MacroScriptTemplateLarge.png
MacroScriptTemplateSmall.png
MacroScriptVBScriptLarge.png
MacroScriptVBScriptSmall.png
MacroScriptWASPPowerShellLarge.png
MacroScriptWASPPowerShellSmall.png
MacroScriptWMILarge.png
MacroScriptWMISmall.png
MobaxtermLarge.png
MobaxtermSmall.png
NavicatPremiumLarge.png
NavicatPremiumSmall.png
NetopGuestLarge.png
NetopGuestSmall.png
NetsupportManagerLarge.png
NetsupportManagerSmall.png
NomachineLarge.png
NomachineSmall.png
NxClientLarge.png
NxClientSmall.png
OfficeWord,ExcelAndPowerPointLarge.png
OfficeWord,ExcelAndPowerPointSmall.png
PdfLarge.png
PdfSmall.png
PenguinetSshClientLarge.png
PenguinetSshClientSmall.png
PgadminIiiLarge.png
PgadminIiiSmall.png
PowertermProLarge.png
PowertermProSmall.png
ProxyNetworks-ProxyMasterLarge.png
ProxyNetworks-ProxyMasterSmall.png
RemoteUtilities-ViewerLarge.png
RemoteUtilities-ViewerSmall.png
Remoteassistant365Large.png
Remoteassistant365Small.png
RoyalTsLarge.png
RoyalTsSmall.png
RvtoolsLarge.png
RvtoolsSmall.png
SapGuiLarge.png
SapGuiSmall.png
SapNetweaverLarge.png
SapNetweaverSmall.png
Sccm2012RemoteControlLarge.png
Sccm2012RemoteControlSmall.png
SecurecrtLarge.png
SecurecrtSmall.png
SecurefxLarge.png
SecurefxSmall.png
SessionADConsoleLarge.png
SessionADConsoleSmall.png
SessionAddOnLarge.png
SessionAddOnSmall.png
SessionAppleRemoteDesktopLarge.png
SessionAppleRemoteDesktopSmall.png
SessionAwsLarge.png
SessionAwsSmall.png
SessionAzureLarge.png
SessionAzureSmall.png
SessionAzureTableStorageLarge.png
SessionAzureTableStorageSmall.png
SessionCitrixWebLarge.png
SessionCitrixWebSmall.png
SessionCommandLineLarge.png
SessionCommandLineSmall.png
SessionComputerLarge.png
SessionComputerSmall.png
SessionContactLarge.png
SessionContactSmall.png
SessionCredentialLarge.png
SessionCredentialSmall.png
SessionDamewareLarge.png
SessionDamewareSmall.png
SessionDataEntryLarge.png
SessionDataEntrySmall.png
SessionDataReportLarge.png
SessionDataReportSmall.png
SessionDatabaseLarge.png
SessionDatabaseSmall.png
SessionDeskRollLarge.png
SessionDeskRollSmall.png
SessionDocumentLarge.png
SessionDocumentSmall.png
SessionDropBoxLarge.png
SessionDropBoxSmall.png
SessionFtpLarge.png
SessionFtpSmall.png
SessionGatewayLarge.png
SessionGatewaySmall.png
SessionGroupLarge.png
SessionGroupSmall.png
SessionHostLarge.png
SessionHostSmall.png
SessionHpRgsLarge.png
SessionHpRgsSmall.png
SessionHyperVLarge.png
SessionHyperVSmall.png
SessionICALarge.png
SessionICASmall.png
SessionInventoryReportLarge.png
SessionInventoryReportSmall.png
SessionItermLarge.png
SessionItermSmall.png
SessionLogMeInLarge.png
SessionLogMeInSmall.png
SessionPCAnywhereLarge.png
SessionPCAnywhereSmall.png
SessionPlayListLarge.png
SessionPlayListSmall.png
SessionPowerShellLarge.png
SessionPowerShellSmall.png
SessionPuttyLarge.png
SessionPuttySmall.png
SessionRDPConfiguredLarge.png
SessionRDPConfiguredSmall.png
SessionRadminLarge.png
SessionRadminSmall.png
SessionRemoteAssistanceLarge.png
SessionRemoteAssistanceSmall.png
SessionS3Large.png
SessionS3Small.png
SessionSNMPReportLarge.png
SessionSNMPReportSmall.png
SessionScreenConnectLarge.png
SessionScreenConnectSmall.png
SessionSessionToolLarge.png
SessionSessionToolSmall.png
SessionSkyDriveLarge.png
SessionSkyDriveSmall.png
SessionSpiceworksLarge.png
SessionSpiceworksSmall.png
SessionSyncLarge.png
SessionSyncSmall.png
SessionTeamViewerLarge.png
SessionTeamViewerSmall.png
SessionTerminalConsoleLarge.png
SessionTerminalConsoleSmall.png
SessionVMRCLarge.png
SessionVMRCSmall.png
SessionVMWareConsoleLarge.png
SessionVMWareConsoleSmall.png
SessionVMWareLarge.png
SessionVMWareSmall.png
SessionVNCLarge.png
SessionVNCSmall.png
SessionVPNLarge.png
SessionVPNSmall.png
SessionVirtualBoxLarge.png
SessionVirtualBoxSmall.png
SessionVirtualPCLarge.png
SessionVirtualPCSmall.png
SessionWebBrowserLarge.png
SessionWebBrowserSmall.png
SessionWindowsVirtualPCLarge.png
SessionWindowsVirtualPCSmall.png
SessionXWindowLarge.png
SessionXWindowSmall.png
SessionXenServerLarge.png
SessionXenServerSmall.png
SmartftpLarge.png
SmartftpSmall.png
SqlServerManagementStudioLarge.png
SqlServerManagementStudioSmall.png
StatusAddOnMissingLarge.png
StatusAddOnMissingSmall.png
StatusConnectedLarge.png
StatusConnectedSmall.png
SupermicroIpmiUtilitiesLarge.png
SupermicroIpmiUtilitiesSmall.png
SyncActiveDirectoryLarge.png
SyncActiveDirectorySmall.png
SyncCSVLarge.png
SyncCSVSmall.png
TeraTermProLarge.png
TeraTermProSmall.png
TextLarge.png
TextSmall.png
ToadLarge.png
ToadSmall.png
VisioLarge.png
VisioSmall.png
VmwareHorizonViewClientLarge.png
VmwareHorizonViewClientSmall.png
VmwareRemoteConsoleLarge.png
VmwareRemoteConsoleSmall.png
WinboxLarge.png
WinboxSmall.png
XmailManagerLarge.png
XmailManagerSmall.png
XmanagerLarge.png
XmanagerSmall.png
XshellLarge.png
XshellSmall.png
ZocLarge.png
ZocSmall.png
Splashscreen
It is possible to personalize the splashscreen by adding a splashscreen.png file in Images\Themes The recommended size is 520 by 320 but the window will automatically adapt to the image.