Unfortunately, applying an effect separately to sprites versus background layers isn't as useful as it sounds; a lot of games use non-animated sprites to touch

Unfortunately, applying an effect separately to sprites versus background layers isn't as useful as it sounds; a lot of games use non-animated sprites to touch up the grid-like nature of background tiles (so treating them separately would look weird), or use multiple sprites to make up a larger character (so treating sprites individually would look weird). I think one of the NES MegaMan games even has a boss battle where the boss is actually a background, and the platforms MegaMan stands on are sprites.