Cremated remains (or "cremains") can be used to create many beautiful objects. Sometimes the ashes are encased in glass or metal, or sometimes they're transformed into something completely different.
Fine Art Etchings
Greyboy Pet Prints makes beautiful, hand-pressed fine art etchings, and for an extra special touch, she can incorporate a tiny bit of your pet's ashes into the ink!
Glass Memorials are a great way to infuse the ashes directly inside a small art piece or custom jewelry, or create an urn to hold the ashes.
Reliquaries are objects meant to contain "relics" or something treasured. They are often presented as jewelry pendants.
Metal-worker, Lisa Havelin, makes beautiful, custom reliquaries that can hold ashes, hair, feathers, whiskers or a photograph.
Additionally, there are a number of reliquary options on etsy.com
The carbon in ashes can be used to create crystals or diamonds. Through heat and pressure, they're transformed into real, certified gems.
There's even a growing trend of mixing cremated ashes with ink, and getting a tattoo. Check with your local tattoo artists to see if this is a service they offer.