The ones I really like from jeans keep lots of the details - back pockets, contrast stitching from the jeans seams, decorative stitching or embellishment on the jeans.
You can also cut a variety of size squares from the jeans, and put them together into one bigger square - for example, a nine-inch square sewn to a 3 x 9 rectangle, then sew three 4 x 9 rectangles together - you end up with 2 blocks that are the same size, sew them together into a bigger block.
The most important thing - have fun!