Plus, I found a really beautiful wooden frame (with mass-produced artwork) at a yard sale for $1, when it originally sold in stores for $40! The glass was missing, but that was perfect for me since I wouldn't be using it anyway. It was a metallic silver color, so I just spray painted it white. (Sorry, no before picture... I blame my impatience!) At the very same yard sale I got a big basket full of seashells for $1, too! I purchased some burlap at a local fabric store, and used the artwork (flipped over, so it was plain cardboard under the burlap) and cut the fabric so it would wrap around a few inches on each side. I laid out the seashells and took a picture so I would remember the placement I wanted.
I wrapped the burlap around and hot glued it to the back of the cardboard. I had to trim the corners a bit because it was too bulky. Then I rearranged the shells, checking with my photo to make sure they were where I had them before. One by one I glued the shells to the burlap. I rubbed the glue in through the burlap to make sure it would stick to the cardboard so the weight of the shell would not pull the burlap away from the cardboard when it was hanging.
I love three dimensional art!