44 pictures of various plants from Franklin Park Conservatory in Columbus, OH. (http://www.fpconservatory.org/)
I've used some of these pictures when introducing/discussing plants over the years. Thought they could potentially be of use!
Note: Unfortunately, these plants are NOT labeled. You may have to do some research on your own if plant taxonomy is your focus.
Note2: This is a large file! (Zip contains 44 .jpg images)