If you have a Generation III Prius (2010-present) with 15 inch wheels, you can pop off the UGLY wheel covers to release the alloy beasts underneath. Except - you'll have a hole in the center of the wheel that begs for a decorative cap. These are based on precise measurements of Toyota part #42603-52110.
This has the symbol of the Decepticons: "The Decepticons are a malevolent race of robot warriors, brutal and merciless. The Decepticons are led by a single undeviating goal: total domination of the universe." http://tfwiki.net/wiki/Decepticon
Nylon is NOT UV stable. For maximum longevity and downright good looks, you will want to paint this object. Acrylic paints with a glossy topcoat are a proven method of painting objects printed using Selective Laser Sintering.
Shapeways has a tutorial here: http://www.shapeways.com/tutorials/painting3dprintedsls
And a blog entry here: http://www.shapeways.com/blog/archives/129-painting-your-3d-printed-models.html
Further, you can locate the recommended Tamiya paints here: