I love, love chalkboard walls! They're the answer to blank space, constant entertainment for the little ones, and with chalk markers, you don't even have to worry about the dusty mess that used to come with chalkboards. I think it'd be so fun to have one in a bedroom or playroom! The trick to making sure the room is still bright and cheerful is just to limit it to one wall, or even half the wall - look at some of these fun shapes!
And if it seems like too much of a commitment to paint the wall itself, you could still get the fun play space by doing an oversized, framed chalkboard. Chalkboard paint means that basically anything can be turned into a creative surface!