And here are two that I did as demos for my Postcards class. The project is to work on 8"x12" paper, and make a composition such that each quarter is different. Then you cut the piece into quadrants and you have four different postcards, 4"x6". That is the challenge: the postcards have to look like they did not all come from the same piece. It's a lot harder than it sounds.
I have not cut these into quarters yet, and I may not do so. Often when I work this way, trying to get each quarter different, with no Unity, Balance, Etc. in mind, I come up with pieces that I find really interesting.
Here they are "cut", in Photoshop, into quarters. Here is the first one:
And the second one: