Do you have a sketch or photo you're working from? I'd break that down to logical layers, test fabric colors/patterns against them. Basic color rules apply, pastels make calming still backgrounds, deep colors towards the front draw you in. I'd avoid a lot of complex angles and tight curves for a first try.
Joan Blalock's book, Quilted Landscapes, has some great tips and easy embellishment methods. Definately worth looking through before you start.