Chain stitch is an interesting one to work. While it's simple in its execution, indeed many of us may have worked it at school, or as one of our first embroidery stitches, it works well either as an outline or filling stitch, and it also looks good scattered around as a detached seeding stitch.
If you're not familiar with the stitch, or want a bit of a refresher, take a look at Sharon B's Stitch dictionary, or Sarah's Hand Embroidery Picture Dictionary. Sharon B also lists other stitches in the chain family which you might want to try.
Here are some examples from the internet of what people have done with chain stitch:
|The Colours of Life: by WiredWitch on Flickr|
|Chain Stitch by Viv Denscombe|
|Chain Stitch on Red: by jacquedavis on Flickr|
|Keychain: by hetkabinet on Flickr|