From 1998 through 2007, I created literally hundreds of illustrations for Pima County's Sonoran Desert Conservation Plan. I painted everything from native plants and animals to ancient pottery and entire ecosystems. Here is tiny fraction of that body of art:
Each individual item was painted with acrylic on paper. I then scanned them, opened them in Photoshop and used some of them over in multiple illustrations. For instance, the Longhorn sheep is in two of the illustrations here.