This is where your imagination should run wild. Get a pen and paper and get sketching, draw out every crazy shape you can think of and refine it, then refine again. Whilst a production board’s shape is largely dictated by the need for a sidecut in order to get some semblance of control on piste, like a surfboard as long as it’s longer than its wide your only limitation is yourself.
Will you be traditional and go long and thin? Or instead opt for the short and fat approach, a la the YES 420. To swallow tail or to taper? Pointy or blunt nose? If you can imagine shredding the deep stuff on it, it’ll probably work.