Got a little story that may help you ID the photo if the facial comparison isn't good enough...in addition to some footwork I explain below there is a forensic organization called "F.A.C.E.S" that may compare the photos and give you an opinion but probably at a price. If your really interested you should send the photo to them to see if they can do anything.
Where did you find the pic? Family photos? The person you found it with could lead to family members which would be just as good as an ID if the genealogy is in place...
I am into the genealogy pretty deep and have had the pleasure of trying to ID photos of dead relatives using 80-85 year old grandparents, aunts, and uncles and distant relatives photo albums. Found this photo in the collection of a distant relative on Long Island and actually ID'd it through military records, and known photos
The man in the photo is my gg grandfather Henry James Warren Pvt. 120th NY Co A. The photo was taken at a photographer of the time on State St, in Albany. The back of the photo read "Christopher Warren" in pencil with the name Christopher rubbed out with an eraser. After looking at the photo we realized that the man was wearing a Union uni (holding hat in right hand...but I think that those old photos are mirror images so he was actually holding the hat in his left). Long story short not all the Warren boys from Ulster County served in the war and Chris was one that didn't. Whoever ID'ed this pic the first time ID'ed it wrong. I had all the Warren boys service records pulled and only one spent time in Albany while in service...my gg grandpa. In fact I can't find any records civilian, military, or otherwise that put any one of them in Albany but my gg grandpa. Thus we put a name with the pic. You might be able to do something similar with the photo if you can place it with a collection from a particular family then compare it to photos of other family members, service records, and census records. I feel very lucky to have this photo as I have heard most privates never had their pics taken with their unis on unless it was a group pic. Most of the single soldier pics in existence are of high ranking officers. Happy hunting and I hope this helps.