The Necklace of Princess Fiorimonde, and Other Stories by Mary De Morgan on Project Gutenberg
Mary de Morgan: Subversion through Fairy Tales by Marilyn Pemberton
The Orchid Album, Vol 1 ; The Orchid Album, Vol 2 by Robert Warner and Benjamin Samuel Williams and Thomas Moore
There are over 40 colored plates in each of these two volumes.
On Project Gutenberg.
U.S. Department of Agriculture (USDA) Pomological Watercolor Collection
This is an amazing collection. There are over 7,000 images in this searchable database.