Inspiration Saturday: Back in the future

I've just finished up the main leg of a Fabric Shop Hop here in Austin, so I have sewing on the brain.  I was most uncharacteristically restrained and only bought a few new fabrics for my stash.  Tomorrow we're going to visit one last shop, though, so I shouldn't speak too soon.

Of course, I tell myself that I will make lovely things out of all of my stash.  Many new project ideas are swirling in my head.  But the pragmatist in me is also inspired by finishing the sewing I've already started.  That is, I'm thinking about what the back of my Taking the subway to Sewing Town quilt is going to look like.

As a reminder, here's how the front turned out:

I bought some batting the other week, and I also picked up yardage of four of the fabrics I used on the front as fat quarters:

I bought extra extra of the one on the far left, because I think it would make an adorable box pleat skirt.  And now I'm thinking that because the other three are so predominantly gray, I should just stick with those three for the quilt back.  I have a yard and a quarter of each, which should be more than enough.  Now I just have to figure out how to put them together.

So right now I'm dealing with a 'fun' (read: torturous) puzzle.  And I'm having flashbacks to old math classes as I work out the measurements.  I've done some quick Google searches and Pinterest browsing for quilt back ideas, but I'm open to suggestions.  What do you think?

And once again, shoutout to Woolen Diversions, the founder of Inspiration Saturdays!