The renowned Art Nouveau jeweler Georges Fouquet (1862-1957) created exquisite enamel jewels representing landscapes and portraits designed by Alphonse Mucha.
Eugene Feuillâtre (1870-1916) also designed enamel jewels.
René Jules Lalique (1860-1945) was renowned for his enamel jewelry :
The Masriera brothers also used enamel to decorate theirs designs.
Sources : Bmjnyc.com , Oxford dictionary and Pinterest