After consideration I decided that the tree would be a good motif to use for an art nouveau wallpaper- with curved and flowing lines to create the branches. Keeping the natural colours of autumn with brown, orange and gold on cream.
I think the colour palette you discussed would work well with the Art Nouveau concept. I think you could still use some of the sketches on the left if you wanted, they are very strong and decorative concepts. I like the leaves and vines very much, it looks quite symmetrically balanced and aesthetically pleasing to my eye.
I think the top 2 sketches could work will as a background theme muted down. Or the leaves pattern you have there. Very good though!