Don't be afraid to use the more traditional colors and patterns that are associated with the Wizard of Oz. By incorporating the red (ruby red slippers), blue and white gingham (Dorothy's dress), yellow (Cowardly Lion), silver or gray (Tin Man), etc. the quilt may match the rest of her collection better. Just because those colors aren't in these blocks doesn't mean you can't use them. We all know what colors are traditionally seen in the Wizard of Oz and so those colors will look natural with your blocks.
By the way, I love the sepia-tone pictures!
Whatever you decide, I am sure your friend will love it!