I don't think it's that the variety doesn't translate to the game, I think it's more just that this kind of mix-and-match approach doesn't generate anything that creates a strong perception of variety. Once you see one stegosaurus-headed thing, anything else with a stegosaurus head looks familiar even if this time it's got painted toenails or a floppy tail.

The result invariably looks about as exciting as one of those mix-and-match flipbooks: https://s-media-cache-ak0.pinimg.com/236x/de/a7/7d/dea77dbbf...