The middle block doesn't bother me since it's central, but I agree that the one to the left of the center is a little too dark compared to the others, you should see if you can switch it out with another that balances better with the rest. Oh and the one in the top left corner, you show rotate two diagonals because you have a square with all the same fabrics in the middle, which you don't have with all the others if that makes sense .... Other than that I love it!!
Rachel