Make simple rectangular tags on a computer (ours have coral-color words and aqua borders). For notched corners, clip with a 1/4-inch hole punch. Apply an adhesive dot to the shell's flattest part; it's removed easily, so guests can have their shells to take home.
One stand will hold six cards and stretch to about 25 inches. If you want a shorter one, subtract 7 inches from card-stock length for one fewer space.