Shell Tablecloth Weights idea from Country Living - Nice for buffet table, but I don't think I'd like them on dining table. "Prevent tablecloths from billowing. Gather sun-bleached oyster or clam shells, sides still attached. Slip jute, knotted at both ends, between open "wings" of the shells, and lay across the table". Read more: How to Decorate with Seashells - Decorating with Shell Crafts - Country Living
Create simple napkin rings < Decorate objects with beautiful shells - AllYou.com Drill tiny holes in individual shells and then string the shells onto twill tape. Tie them around napkins in a complementary color. Use a craft drill to make the holes in the bottom of the shells.