I need help with Default.png On my Windows XP Theme.

[Patmurph245]

My names pat. i'm 15 and about 2 months ago i Jailbroke my ipod touch 1st Gen.
I tampered with everything here and there, and created my very own Windows xp theme with the help if Paint.NET and the print screen button.
Anyway. the first attatched image shows my home screen. when i tap on Microsoft word, it brings up the Default.png Image which is the second attatched image (The icons are apart of the image).
My question is, i want to rotate the Background of my Theme every minute or so, and when i make everything around the splash screen transparent it becomes black.
How would i work around this?