I talked with Wayne Turner who is doing fine work in El Dorado also photographing tombstones of Civil war Veterans. He said that he will be posting Greenup Mercer's tombstone photo shortly. I will remind him. Wayne has documented most of Butler Counties Civil war Veterans and has alot of information about them. Wayne said that he would post it on the Flickr Group: Civil war Veterans Buried in Kansas: http://www.flickr.com/groups/civil_war_veterans_kansas/
I am also interested in the photo that you said that you have. If you could scan it and email it to me I will post it on Civil war Veterans Buried in Kansas and I will have a friend post it on the National Flickr Group: Veterans of the American Civil war:
http://www.flickr.com/groups/veterans_of_the_american_civil_war/