You could work out the size of your largest block, then make scrappy/randoms out of the rest (adding bits and pieces 'til they are all a uniform size). Pick a nice bright solid (black is my all time favourite) sash them, say, an inch and a half all the way round and there you have it.
I am doing one at the moment and since it is going on our bed, I got my husband to pick the sashing (he went with red)...he also got the most peculiar Wizard of Oz fabric (demented looking trees with faces) and red apples...looks quirky and that will be the backing. It is purely an exercise in loosening up, improving my skills and depleting large amounts of bits and pieces. I also want to see if I can quilt a queen size quilt on my domestic machine, without messing up. Let us know how you get on....it is fascinating to see what different quilters get up to!