You can paint the kids room door! They can put there drawings up make little sayings like "No Boys/Girls Allowed!" (Always my favorite HA), you can even choose to make a chore list on the door and have them erase when they finish it.
Here's a great idea if you don't like the look of the painted wall, build a shape out of wood and paint the front, let them use their imagination to draw in what it should be!
The bottom half of the hallway wall is a great place to put chalkboard paint. They can easily reach and they can put up drawings for your guess' that come into the house.
I think this is the most creative yet! For those of you with a little artistic side you can draw a face on a clipboard and let this kids draw in the face!
This is a cool idea for them to customize their piggy banks the way they want. They could even do little money signs =)
I love this idea here. More localized so you don't have to really change the look of anything you have. Paint the top of a round table with a hole in the middle for chalk and move to where ever the kids want.
Last but not least, paint the bottom portion of your kitchen island for kids to draw while your cooking or to put a menu or even draw different foods for a different look to the room.
All of these are great ideas to keep your kids busy and out of trouble! You'll never have to scrub your good walls again because they'll have their own to draw on!