I've mentioned this site before, but in case you are trying to find art ideas for kids without going to the library, please check this out: http://www.artprojectsforkids.org/
Art teacher Kathy Barbro has made templates for wall murals, downloadable to your printer. (Each section of the mural is printed on one page; you color them and then assemble.) These are really big and if you have a large wall or table where your kids could work on it, it's sure to keep them busy and productive for a long time. Templates are $5 and sent by email. Don't worry, there are plenty of free ideas there, too.
Since this upcoming school year I will be teaching world history and geography (slanted, I plan, toward geography) I wanted to incorporate as many art projects from world cultures and artists as I could. I also want to bring in special guest speakers whom I know personally have either lived in or traveled to certain countries. One of these people, Katrine, was born in Belgium. I was tickled when, after asking God to show me a fun art lesson about a Belgian artist, I landed on this site again and immediately found a project called An Eye for Magritte. All you need is a piece of white paper, a CD, and colored pencils. Very cool. Can't wait for Joel to try it.
One more thing: if you're teaching world geography, you might want to request the passport template from Art Projects for Kids. Again, only five bucks. I'm going to do that since we will be travelin' Around the World in 80 Days (Give or Take 50).