"...there are no known photos..."
We have been blessed with pics in our 7th Mississippi research. I believe most have come from descendents. I can't over emphasize having a website with a unit roster. Folks search Google and other search engines for their ancestors names and when they find the name listed on a website that is asking them to help I find we have had a 100% success rate in dealing with these folks.
Never underestimate the internet :-)