Armylady - the sky is the limit!!! Well, actually there are some limits in sizing LOL but otherwise, it's a free for all in design, shape, etc. If you look through previous threads under the swap, you'll see some awesome examples of wall hangings!
Ube got one of mine that was likely way to big for a wall hanging, but I got carried away!!!! (remember that one Ube? with the embroidered flowers LOL)
Welcome, and just be as creative as you want to be!