It is gorgeous! Great choice of fabrics too! Our group made a NOEL table runner (except I altered my design) where the pieces kept escaping from under the black bias, in the end, I used ALOT of black thread & did fancy stitching over the whole bias that made it look a little lacy but held the fabrics in. One lady just made a backing & envelope type finish and used it for a door hanger, so she didn't mind that the fabric was pulling away. We all agreed if we were to try an intricate design again that we would add about 1/8th" around the whole shape first so the actual pieces would overlap a little before placing the leading on them.
Did you fuse the shapes down first ?