I think it is safe to give jewelry for the newlyweds as a gift especially when you are not very sure of what to give or most of the items in their registry had been taken. It is a nice gift to consider like how my husband and I prefer to give our newlywed friends or relatives jewelries instead to commemorate their union in a very special way.
Good example of jewelries you can consider as wedding gifts are:
Take for example these masonic rings at joyjewelers.com. They are pretty and unique and when you offer to give the wedding bands instead, you're actually helping the couple save some money as long as they are willing to take the offer.
Pendants are another great jewelry gifts for the newly weds. You can choose to give their initials or 2 hearts or even a pendant with special inscription of Mr. and Mrs. That will certainly make them appreciate the token.
If you prefer to give them necklace then it is also a nice wedding gift to offer. You can get them a "for him" and "for her" style of necklace so they can wear it with pride.
(all photos from joyjewelers.com)