A few nice wallpaper background images I found:
CPU Wallpaper w/circuits 
Image by somegeekintn Some wallpaper I made for my iPhone. Feel free to use it if you like.
Polka-dotted background for twitter or other (Pink) 
Image by momo_mika Polka-dotted background (Pink)
Polka-dotted background for twitter or other (Red) 
Image by momo_mika Polka-dotted background (Red)