Collages work nice with this age. You can do a theme related background if you wish. If you don't have a theme you might want to do a color collage. Provide a specific colored background and the corresponding colored items to glue onto the background.
I agree with fingerpainting. Any kind of painting for that matter. Another activity that you can vary so much. Can use finger painting paper, you can use corrugated cardboard, theme related shapes, regular cardboard, fat and skinny brushes, 2 primary colors, home made paint tools, you can add texture to the paint etc.
Another favorite amongst my group is sand art. I give them a bottle of glue and let them go. They do use lots of glue but it's the process that matters...not the product (but the ending pieces is usually pretty nice). It strengthens their hands-the explorations teach them that if I squeeze this really hard a lot of glue comes out...if I don't only a little glue comes out, etc. This is all necessary for future projects. A black background is great because it contrasts with the glue as well as with the sand. I usually have them use their pincher fingers and only give them a little sand at a time in their own individual containers. Some will try to dump it all in one spot. They will do the same with the glue so encourage them to move the glue all over the paper, not just in one spot. :-)