It is not clear from the picture, but he seems to be an enlisted man and as such it would likely be a DI (Distinctive Insignia) -- AKA the "insignia" for the unit he was assigned to. A sample below:
The photo is difficult to make out, which is pretty much the norm for 75 year old pictures, but try going to ACUARMY dot com and click on Army Unit Crests. They have several pages of DUI's. If you can rescan a closer view it might show a bit more detail. Good luck and keep us informed.
Given the original poster's avatar, I initially assumed that the fellow in the photos was USAAF. Any background information would help substantially narrow the options down. Do you know what branch he was in, and/or what theatre/locations he served in?