The Garage is a "mechanic's garage" where you can build custom cars. It currently costs 300 gems to unlock. It's possibilities range from upgradeable parts like Inline 4 engines to Diesel V8 engines, along with different types of body frames, and even different kinds of tires.
The Jeep body, (shown below) is a basic body for a custom car. It looks and acts like the normal Jeep. The Jeep body is a common car body found in gift chests.