I know you want to keep those blocks intact, but that black border really needs to be around the Batman squares in order to be effective.
Leaving it where you now have it, around the blocks. just makes breaks up your one busy quilt top into 20 busy blocks.
All three fabrics are the pretty close in value, which is why you can't distinguish any one of them.
If it were my quilt, I'd surround the squares with black and them maybe blue to give it some more interest.
Then put the the other fabrics around them to make a bigger block.
You might have to do some recutting, but those squares would really show well.