Treadwell's Jewelers will monogram your shell pendant for free!

Monogramming comes in various styles and colors, most commonly it is black or brown in color in a script font. 

You can have a single letter monogram or select a 3-letter monogram.  In the 3-letter monogram, the last name initial is in the middle and in a larger size, as depicted here. 

Also available, but not depicted, is a school monogram or sorority letters.  Images would have to be provided for special monograms.