Shadow box quilt happiness

So...here is a look at my shadow/shadow box quilt in progress! It is actually turning out as I imagined and I am really pleased. I have three more rows to go, plus the sashings and border. I am planning a plain white border to match the sashing, but haven't decided on any additional border(s). I'm considering a thin gray strip to mimic the "shadow" on the blocks, but don't have a clue what I would use after that. (The charm material is Kim Schaefer's Tic Tac line for Andover fabrics.) Any suggestions???

Excuse the cat, Zorro, in the background. He is always so helpful! And the pool table was the easiest place to spread out the pieces. Not very elegant but it works!