I've been squinting at your block (I know, I must look a little weird
) and I like the background you have as it makes the design feel like it has the night sky full of stars as a background. The print is also quite small so I think it would like beautiful once all the blocks are joined together. At the moment, the lower contrast and patterns in the block give it a sort of boho feel, which is what I love. However, if you feel you want more contrast then I would probably go for the steel gray or a slightly lighter gray. Could you do a mock up on your computer to get an overall effect of your background colours?