Danny,
Its not cheap, but Jim Gordon's 3 book set Great Gunmakers For the Early West has color photos of about 20 Deringer rifles in it, plus smoothbores, Deringer NW guns, and military guns. That's likely the best resource out there on Deringer rifles, but the 3 books run close to $300. There's also a couple of Deringer rifles pictured in Garavaglia and Worman's book 'Firearms of the American West 1803-1865'. And Charlie Hanson's writings in 'The Northwest Gun', the Plains Rifle, and the Museum of the Fur Trade Quarterly all have some info on War Dept and Indian Trade Bureau orders for his guns. One of the Book of Buckskinning series also has an article by Hanson that has a Deringer smoothrifle pictured in it with a small eagle-head patchbox.
I really like Deringer rifles. Send me a pm with an e-mail address if you want to chat about them.
Sean