We live near the beach where the most common shell is the oyster shell. The oyster just happens to be our state's official shell. I like the ones off the beach because they have been rolled smooth and clean by the sea, not to mention the exercise and relaxation gained by hunting for them. If you have access to these shells, there are some creative ideas which blend well with cottage/bungalow chic or the shabby decorating style:
Christmas ornaments: Drill a hole in them and hang them on your Christmas tree. These are even more beautiful under the twinkly lights if you paint them with decoupage type glue(watered down Elmer's) and sprinkle with white glitter. I sprayed mine with a clear paint to seal the glitter.
Oyster shell mosaic tables. I saw this in the most recent Allposter.com catalog. All you need is some tile grout and shells. This could be done on just about anything. See the oyster shell fireplace front for another mosaic idea , click to enlarge.
Shell jewelry is always fun. I look for flat small oyster shells(or pieces which have been worn smooth by the sea) with natural holes(or drill your own hole) and string them through a silver chain. You can dress up earrings this way as well, just slide them on to hoop earrings. Limpets are good for this as well.
Click here to see an all white oval shell mosaic mirror done mostly with oyster shells.
Finial Dressing: Shells look very pretty knotted on long ribbons which hang off the curtain rod finals. I've done this in the past with an oyster shell at the bottom.
Garlands: use parts of oyster shells that you find on the beach, drill holes in them and knot them along a long ribbon. In our first apartment, I strung the shells along white, creme and pale pink satin ribbon, very pretty. I don't have a picture of them, but I found this picture of a cowrie shell garland.
I've also done wreaths with oyster shells, used them as candle holders for tea light candles, and as soap holders(drill holes for drainage) . These shells would be beautiful grouted onto a wood cross using driftwood(straight and nailed together) or cut plywood. Whatever you do with the shells, they look better with a shabby chic edge; pair them and craft them with weathered and white items. If you start combining unnatural colors with them they just end up looking like garish elementary school craft items, and maybe not so chic.
Here's an idea from Catholic Traditions in Crafts, Baptismal Shell.
A Marian Grotto that you could reproduce with shells.
Religious symbolism: "Clam shells, scallop shells, and other types of shells are a symbol of a person's Christian pilgrimage or journey through life and of baptism in the church. In the middle ages, Christians wore the scallop shell to indicate that they had made a pilgrimage to the shrine of St. James of Compostella in Spain. Placing a shell on a gravestone when visiting the site is an ancient custom and may in fact have several different meanings depending on the cultural background of the people placing the shells. The idea of crossing over a body of water to the promised land or crossing the River of Styx to the afterlife, the final journey to the "other side" is also part of the symbolism of the shell." ~ Assoc. for Gravestone Studies.
Shells are also symbols of life and resurrection, and baptism. The water of the ocean is symbolic of God's unlimited knowledge.
Shells always remind me of grottoes and the 18th century Rococo style(a combination of the French rocaille, or shell, and the Italian barocco, or Baroque style)' one of my favorite design styles. Rococo has a love of shell-like curves.
Shell lined grotto in England, Goldney Hall.