Oh, that's really pretty! Are you up for FMQ? If so, I'd do curlicues shaped like question marks from the center of the block out. Or you could go from one point of the triangle to the others by curving the stitching in towards the center of the triangle, then back to the next point. I'd probably do more curlicues in the borders. Feathers on the borders would be really pretty (I haven't attempted those myself yet).