I am using the custom theme and the file “ImageCache.png” to set the theme. It appears some of the additions and modifications of version 3.2+ (I am using the latest v3.2.1) have damaged the custom theme from v3.1.3 on both Windows and MacOS (haven’t tried updating on LINUX). I completely uninstalled Audacity on Windows and cleaned up as much as possible for a new install of Audacity v3.2.1 and I see the path to the custom theme has adjusted slightly but moving an old (v3.1.3) ImageCache.png to this location has a lot of bad results on the Audacity interface. The new v3.2.1 didn’t place an example ImageCache.png in the folder to use to modify (that would be a solution). Maybe someone has this new version of ImageCache.png to help create modified custom themes?
This issue has been reported to the developers here: ImageCache.png needs updating · Issue #3760 · audacity/audacity · GitHub