Is there an order to your FQ's, in terms of the placement? Even if you do a 4x4 setting, can't you use some of the fabric from the other 2 FQ's in some of the blocks for more variety?
I made these blocks all the same so I can't comment on how 18 different colors and/or patterns would look without seeing your fabric, but here are the two block layouts:
Well, I tried to upload the 2 pics and it keeps timing out on me. I'll try in another post in the morning.