Start playing with the HSTs. There are a lot of blocks that use them. You could make a sampler quilt of all kinds of blocks or find one you like and make a quilt of them. There may be 2 that look great together and make a secondary design. Remember that they have to have the same # of components to blend together the best. (ie. 3x3, 4x4 etc.). If you want to keep it simple do a pinwheel quilt.