I love the idea of making mosaics. I think it's particularly challenging for kids to "see" a picture in their minds and then create it using pieces. We used colored pasta to make a picture and then the kids told the story of what inspired them. Before we did this we read the story Legend of the Indian Paintbrush by dePaola, that's where the sunsets came from I think.
If you don't know how to color pasta, it's super easy! You just put the shells in a ziploc bag with a few drops of rubbing alcohol and a few drops of food coloring. Shake, shake, shake. Let them dry (you might want to make sure they separate...sometimes they tend to stick together a little bit). And voila! :)
My favorite--she's very artistic.
This one is God.
It actually kind of looks like the student! :)