We used liquid tempera paint in natural colors to create painted papers for our collage. I have a set of "line tracing" cards (basically just blue credit cards) that I cut to make into paint combs. We discussed texture and what it must have been like to draw on a cave wall versus on paper. Then we made our textured paper. ALMOST too beautiful to cut up. ;)
The next week, we drew images on the back of common cave art pictures like handprints, animals, and stick figures hunting. I tried to get them to understand that we have to make shapes, not lines, to cut out more easily. Some of them understood, others got it once they drew line people and tried to cut it out. It is a learning process. ^_^
Then we crumpled another piece of paper to make a bumpy cave wall and glued our cut-out painted paper shapes on top. I was very happy with their work, they are beautiful.