Hello there!

You are certainly permitted to provide photos here. The restriction is simply that the post must be a Reddit "text post" rather than a "link post": you can provide hyperlinks to images in the post text (just edit your post to add), or simply "reply" to yourself with a comment.

As for identification/information regarding military personnel, our Guide on Military Identification may be of use to you. It provides a number of different resources, including how to request service records from a number of national agencies around the world, as well as graphical aids to assist in deciphering rank, unit, and other forms of badges or insignia. While the users here may still be able to lend you more assistance, hopefully this will provide a good place to start!