Let the user choose a background instead of just having a dark grey (and some different colour with 'play over desktop' enabled).
Potential options include:
A user-defined solid colour
A user-defined image (so you can pretend that 'play over desktop' works... or just have them fly around a funny image)
Let the user choose a background instead of just having a dark grey (and some different colour with 'play over desktop' enabled). Potential options include: