If you want to add some interesting elements to your garden, then perhaps a landscape rock would be of interest. Home Depot is one store that carries a couple of nice landscape stones and rocks made in high density plastic resin. These rocks are lighter than regular rocks, so you can move them easier - perfect if you're looking for an accent rock in your garden.
It's pretty neat that you can buy these types of rocks that look just like the real thing, however they are much easier to transfer and move around. These rocks come in a range of shades such as sandstone, sand, granite and river rock, so it shouldn't be too difficult to find something that goes with your particular preference. It can definitely be easier to buy one of these light landscape rocks as opposed to going out and trying to find a real one. Have you ever lifted a really large rock? They are surprisingly heavy so it can be quite tricky to get it home, never mind positioning it in the exact right place for your needs. If you're setting up the perfect outdoor setting, perhaps with a small pond or waterfall, then adding some scenic rocks can definitely enhance the setting and over at Home Depot you can find quite a few nice pieces...
Extra Large Landscape Rock, Sandstone
"Emsco is an innovater in the Lawn Decor business and has created another high quality Landscape Product: our Architectural Landscape Rocks made of high density Plastic resin. These decorative Landscape Rocks come in 5 sizes and 2 colors and are perfect to add beauty and definition to any landscape design or to hide unsightly elements such as well covers, pumps, pipes or sprinkler valves."
Large Landscape Boulder, Granite
"Made out of a heavy duty and realistic-looking Plastic Resin, they are very durable but lightweight and easy to install. Be creative around your garden and lawn. Grey granite Color. Covers unsightly elements in your yard like wells, pipes or sprinkler valves"
Small Landscape Rock, RiverRock
Large Landscape Rock, Sand
These rocks can be found at homedepot.com