Product Version: All versions
Updated: November 30, 2017
Desktop Background resets to Citrix theme several seconds after logon. Initially it is possible to see the user-defined background but after several seconds the Citrix default theme background replaces it.
Citrix sets this background via a local GPO. Therefore, disabling that GPO will solve the problem.
1. On your base image start gpedit.msc using Run
2. Local Group Policy will open.
Then User settings > Administrative templates > Control Panel > Personalization > Load a specific theme
Set it to "Not Configured".