OSX 10.7.4 wallpaper reseting??

Alright so I have the new macbook pro with retina display mac osx 10.7.4. I set my background some random image but it was a lo-res so I switched it to another image. When I go to restart my computer each and every time it resets back to that lo-res picture as my wallpaper. So I completely deleted the file and emptied the trash on my computer and yet it still comes up as my wallpaper everytime I reset. When I go to system preferences-desktop&screensaver it shows that my wallpaper is not the lo-res image, but it is. Very weird and confusing not sure how to get around this. Thanks!