I love making tumbler blocks. Anything goes. Just make sure rows are done in uneven numbers so you can adjust to avoid getting two of the same fabric together (not the end of the world if you do, however). The easiest way I've found is to cut pieces 5" x 5" (or left-over charms), trimming the sides at an angle to equal 3" at the top and the full 5" at the bottom. If you do trim off those side pieces, alternate the wide/narrow ends and join them on the horizontal. Trim the sides and you have a ready-made border.
All kinds of variations, but I've found this the great stash-buster, and the no-brainer therapy I need from time to time.
It will all pull together with a same-color, rather solid (or small print) border. You might also want to use that fabric for an inner border before attaching the small pieces.
Try it, you'll like it!