[TXnMA]

Have you tried Bing Image Search? I find it frequently comes up with surprising stuff.

Alternately, do you have distinguishing info, such a unit or battle/camp location for searching WW1 history references -- or old newspaper morgues?

Or, you might try this:

~~~~~~~~~~~~~
The designated repository for all official U.S. military photographs taken before 1982 is the:
Still Picture Reference
Special Media Archives Services Division
National Archives & Records Administration
8601 Adelphi Road
College Park, MD 20740-6001
Web site: http://www.archives.gov/dc-metro/college-park/photographs-dc.html
Telephone: (301) 837-0561
Fax: (301) 837-3621
~~~~~~~~~~~~~

Good luck!!

[TXnMA]

I intended # 11 to be for you...