I just recently saw one where the blocks were rectangular. On the first row, the first block was placed vertically (6 " across x 12" down) then 2 blocks long sides together (now 12 " wide x 12" long) repeat. If you did 6 in, 12 in, and repeated 2 more times you would have 54 inches wide.
ON the second row it started with 2 blocks (12" sides together) followed by a 6" block. Hope this makes sense.
So you would have alternating rows of 6" wide followed by 2 12" wide together, then 2 12" wide, followed by a 6" wide. This way the vertical/horizontal nature of the blocks would add more interest to the quilt.