We have this gigantic calendar in our house that we use in a desperate attempt to keep our lives organized. Once a month, I get to rip of an enormous calendar page, and the Eskimo gets a great big blank canvas. This month, I taped February to the wall and gave him some crayons. He was coloring "on the wall", and he thought it was amazing.
A couple of qualifiers: I don't leave crayons/markers/paints/etc laying around the house. Some folks do, and that's their call, but the Eskimo gets plenty of opportunities to be spontaneously creative; he doesn't need free access to art materials. He also knows where I keep them, so he can come and ask me for access at any point during the day if he'd like to color. So, teaching him to "draw on the wall" is not super dangerous in our house. This was also a highly supervised activity, as are all artistic endeavors in our home. I don't just sit there and watch, I will usually get in there and color with him, whether it's on my own sheet of paper, or sharing with him.
Teaching the Eskimo that it was okay to draw on the wall as long as he kept the crayons on the paper was fun, too. He started walking around the house, pointing at different surfaces, waiting for my reaction. Cabinet? No! Floor? No! Paper? Yes!!! Big smile. He's still working on boundaries and self control, so this was great practice for him.
We left the calendar sheet up for a couple of days and he went back to it many times, adding to his beautiful scribbles. Maybe next month we'll paint!