Ring of fire, Ring of Air, Ring of ?

[Tar-Maglor]

Good question, mate. I personally don't think Celebrimbor would have made a fourth ring. The epitome of elvish artifaction were Feanor's Silmarils, and they were each associated with air, fire, and water. Also, I believe Feanor was Celebrimbor's grandfather, so I think Celebrimbor would have followed in that tradition.
~Cheers!