I have come to this when I tried to play many side-scroller platform games. Horribly frameskip and a fancy but useless background. It's possible to disable some layers and save cpu cycles from rendering them, thus fasten emulation a little.
To be brief:
http://media.photobucket.com/image/snes%20sprites%20disabled/Raccoon_Sam/Layer1_and_2_Disabled.pngSomething like this but in rockboy, of course.
Maybe this could hit Player experience, but its a worth way of improve performance if you know what are you doing.