Just a link for a site with a lot of photo (from WWII to Afghanistan).
Just a little warning : almost all photo have been taken in "war conditions" and some of them could shock or disturb.
http://otomo68.over-blog.com/categorie-10947077.html
Site in french, i give you some transalation :
guerre = war
societe militaire privee : contractors, mercenaries, ect (Mainly Irak)
Enfants soldats = Child soldier
Malouines = Falklands
Other words are enought close with english to be understand by everybody here.