Lost my deep black homescreen, how do I get it back?

[bczrx]

I have a Sprint TP2 with the Sprint OEM WM6.5 update.

The phone jostled in my pocket today while on a motorcycle ride with the screen unlocked. When I pulled it out the homepage screen had changed to the same image as my lockscreen and start screen. I want to return it to the deep crystal-clear black background it had before. How do I do this without a hard reset?

I've tried the settings, but am not finding anything that is really changing anything.

Thanks!