So I experimented today. I think my biggest problem might be that I can only shop on line, and I'm sure most of you know how the reality can differ from a website photo.
A few years ago, I bought a bunch of half yards of what you could call background solids from FQS, which they were kind enough to label for me. I checked those against my blocks tonight, from whites to the darkest -- 'Putty.' They were all too light, and (as Dunster forecast), blended into the backgrounds of my lighter blocks. The lighter shades were, (as Watson forecast), far too bright, (I'm shying away from the idea of blue; I used a pale blue once as background and it had a very chilling effect.)
I recently bought a Kansas Troubles bundle of creams (their creams tend to be heavier). The darker of these did blend with my darker backgrounds, but one of the lighter ones seemed like a possibility. Here is block with darkest background, KT cream in between, block with lightest background (close-up to show print on cream). The quilt has four blocks with lighter backgrounds. What's your opinion on using a printed sashing rather than a solid?