I think an Ohio Star with some alternating block would look great. If I can get this to work, I'm posting a photo of a quilt I just finished for my son that is similar to what you were originally thinking. I alternated an Ohio Star with a Building Block - both 9" blocks, set on point. This part of the quilt covers the entire top of the bed. Then did a relatively simple border for the part of the quilt that hangs over the sides and bottom. It's a queen-sized quilt, although the photo is taken on a king sized bed, so don't be mislead by the size. But if you enlarge to a 12" block, you would probably have a similar number of blocks, so hopefully this would give you some idea of what it might look like.