Personally I would ditch the purple.
I'd try out something that would bring out the gorgeous tree fabric. Maybe a brown or black or even a white or green.
Looks great to me and I'm not a purple lover. I think you'll like the end product, besides you'll get a chance to use other color combos in another project.
This looks fine to me. It is my daughter's favourite colour combination and I made her one similar to yours to take to college. She has had so many complements on her quilt and you will too!