Here's a photo of an art wall made with white sheets. If you don't have poles to attach the sheets, you can use two easels. Just place one on each end of the sheet. For best results, get some stakes at a hardware store and line up two or three sheets to make a long wall of art. For younger kids, make sure that the sheets are lower. If possible, try to set the art wall up so that the kids can go around it and paint the other side. Or just opt to hang over a fence like we did.
I placed a few paint bins on the fence so its a one stop area and more organized. The kids can play with fun paint props like spray bottles, squirt bottles large rolling brushes and fun paint on decals.