This has turned out so awesome. I would do a thin black border, maybe 1" finished then do a piano key and make it as long as you want to get it up to size but I would make it maybe 3" wide of all those jewel tones. Unless you still have strips cut from your cabins then use those. The width of the piano key border would then be dependent on your strip sizes. Then I would do another thin black just to stabalize the piano key, (or you could stay stitch it) and bind it in black. I love your setting for the LC blocks. The middle part in black reminds me of a compass.
Edited to add, I didn't read any of the responses before posting so will go back and read them now. Apologies if I repeated something someone else said. OK I just went back and read and seems quite a few of us had that piano key idea. I like the idea of the squares too, alternating with the black. Great minds think alike :lol: