I have all my white background fabric cut up and organized too. I decided to go with Kona White, as to not have any other color competing with the main prints. This is my second go around with this pattern and I learned a few things.
My 1/4 inch seams suck even with the guide foot. I try but my HST's usually end up off a bit. I am starching all of my prints and I think it helps big time against my HST distortion. I am starching the cut white pieces as I go. When I press them, I'm pressing them in half too so that way I don't have to mark the lines or use pins. With this block I haven't had to trim much at all which is great. Also, I get really impatient with pressing and sewing and pressing and sewing again so I rush through, not ironing properly. It really helps to press all the seams open and its worth the time & effort.
Peacock Swoon Block #1