Well after reading everything it got me thinking... Couldn't you just add another artwork path that points to a folder of images for each game specifically to load up as backgrounds with the 2nd layer (_FOREGROUND) and load an image to display as the background for each game's rom name? That shouldn't be too hard as it really only adds one field in advanced emu setup (as long as theme elements aren't changed)... Like the controls image it could have a static image too for systems you don't have game screens for? The thing it's though they would need to be consistent with lists and stuff, so this is pretty theme dependent and would be tough to share.