I had my wife's (then girlfriend) engagement ring custom made by a jeweler who is not usually retail, but sold through retail establishments. We have a family connection to them, so they helped me out. They took an incredible amount of time with me, educating me about stones, then working with me on the setting, and picking just the rock for the ring (and the budget). Through our time together, I found that she was a lover of French wines. When the final product came to my door, there was a bottle of very nice Bordeaux going to her. It was a courtesy, and a token of my appreciation and friendship, I wouldn't say a tip.
As they do not take many retail customers, I can't refer many people to her. I do praise their jewelry and service, and when I hear of someone that has a unique or interesting request, I do call her to see if she'd be interested. She's taken me up on that once or twice, and has always been very appreciative.