Oh yes, masks are great. You can use Direct to Paper, chalks, watercolors, anything to add depths.
Here is Michelle Laycock's no-layer swap gallery if you want some more ideas!
My Favorite Creations Gallery at Splitcoaststampers
Also, there is one here with a wolf image that just blew me away! It looked no-layer to me (could be wrong, but sure looked like it), but it was sent as an ecard so I'm not sure who created. You might try a search in the gallery for "wolf". It's definitely worth the time to search for==in fact, I'm going to and add it to my favorites!
Tam