Deeper color would be cool (not that leaving it white is wrong). Hard to comment on what exactly the color should be..can't see your backsplash very well. Would you describe it as grayish blue(that's what I see on my monitor), or..?

why is it trouble that you still like your vintage posters? I think there's no trouble at all..makes all sense when one's attached to the art he owns, otherwise why to have it. I think the poster will work very nice in your kitchen, whether you choose a color or leave it white.

Thanks for your thoughtful response. The backsplash is a glass brick tile with a little texture so no color. My concern was that I updated the kitchen from a traditional cornice to what you see, changed the knobs, etc. but the artwork is very traditional. But, like you said, I love it so it stays! Heading to the paint store to see about a light grass green/gray combo. thanks for your input.