This may not help you for these two quilts but for the future. A lot of the time I choose my backing fabric before I make the quilt to go with it. I pull colors from my backing choice for the top. I am not the best quilter so having a patterned backing helps to hide my poor skills.
Those times I make a top before I have a backing I just take the top with me to my LQS and audition fabrics.
I love the hunt!
peace