My Android phone changed theme

[lily0615]

I have a Samsung Galaxy Prevail and yesterday some little icon popped up saying to download something for my phone that it required some time and could not be interrupted. It kept popping up so i figured it was something for the phone. Once my phone turned back on the theme was different. it had some minor changes and i don't like how it looks. How do I change it back to its original theme? i already tried restoring my phone but that didn't work. Does anybody know how to fix this?:-\