Well, after all the song-and-dance on this blog about what background to choose for my Sunflowers, I bit the bullet, and now I have two options, none of which have been shown before.
Option 1 : Lots of different blues.
Option 2 : A fabric bought the weekend before last, which actually has all the nuances of greens that I use in the flowers proper, and a few more, plus some yellows and blues too, and a big leaves pattern, which will probably be unrecognizable when cut into pieces.
I think I'll go with Option 2, the fabric of the many greens, for the main quilt, and with Option 1 for the 'Reject' quilt.
And no, they are not properly rejected blocks. As was the case with the Passacaglia, there will be blocks that doesn't work with the rest, and the ones that stick out the most will be getting a multiple-blue background and will - eventually - form a quilt of its own ... hopefully a quilt smaller than the one with greens in the background :-)