You would be amazed with what people come up with when it comes to seashells.

One of my favorite ideas is the Sea Urchin Planter.  It can probably house any type of small plant however air plants work best.

It works best with Sputnik Urchins (shown) due to their durability, however any type of Urchin should work fine.  This is probably the easiest DIY shell craft there is!