Have you tried the self-service tattoo lookup on the JC website? They have upgraded it to include partial tattoo searches which you only have to have three characters and a basic despription (gender, color and white markings) to get a list of possible matches that you can then look through and try to narrow it down.
I did learn something in our search for our girl's identity -- if it seems like everything but one item is a match (even something fairly major), it doesn't hurt to e-mail the JC and ask some questions. We kept coming to the same conclusion on our girl's tattoo (multiple people looking at it) and the description for the horse on the JC site matched EXCEPT it stated she was a chestnut and she is very clearly and obviously bay. Big difference, right? We had actually written it off as any chance it was her, then DD came across an old race replay for the horse on the JC site and we could see the horse was, in fact, bay - so I e-mailed the JC and they confirmed there had been a mismark on the foal papers that had been corrected, but the original info is what was listed on the tattoo look-up which still had the incorrect color!
To photograph the tattoo it is best done in a dark area and use of a blacklight can help to highlight the ink. Have at least two people - one to flip the lip and one to photograph. Also, because of the stretch/curve of the area, it can be usesful to break it into two or three sections and photograph it that way vs. trying to get the whole thing in each shot - this allows you to really zoom/focus on the characters you are trying to show and get the clearest shot of each.