Peterstone has now created a line of jewelry based on the work of Courtney Davis! I've known Courtney for a few years now, he's a really nice guy and probably best known for his Celtic clip art books published through Dover. Now you can get jewelry with his art too!
Pop by Peterstone's website to see their entire catalog, they don't just have Celtic stuff, but lots more... dolphins, wolves, rings with stones, pentacles, and more Celtic stuff yet!

Please note that these are just affiliate links for Peterstone... I don't ship or sell their jewelry, I've just set up links to some ones I thought were nice. Any cheques or questions about their jewelry can be directed to Peterstone through their website. :-)