My thoughts...number one...it IS a very nice butterfly pattern and your colors are just perfect. If you are going to use it for a wall hanging it wouldn't need to be much bigger. I would put a 3 inch border next of the lighter turqoise-green print (the same as in the butterfly), a medium larger print next and then a solid. I like to do light, med, dark. The dark could also be the binding. It would add approx 6 to 9 inches all around.
My daughter told me I was making my new baby quilts too big, 45 X 60 crib size...and she couldn't show off the design well enough...so a smaller cover is nice at first. See then you can work on another one for each time the little bundle of joy grows a bit! Can't wait to see how it turns out!