pencil sketches | Pencil Sketches Scenery. Although I don't think the drawing is very inspiring, the idea is quite nice. If i were to do something along these lines i would improve it by using a variety of different tools, not just a pencil.
Set of Shell Sketches - Organic Objects Objects
seashell drawing - Google Search
sea shell stencil - Google Search
Seashells Vintage Images - Love the graphics fairy! (thegraphicsfairy.com)