Aliens. Axed Mustangs. Narrowed Bobs. Flat-bottomed Sporties. Split tanks. 3.5's. Frisco. Deep tunnel. Flaked. Molded. Peaked. Flamed and scalloped. Patina. Fauxtina. The ubiquitous Wassel. There is no end to the gas tank styles to choose from, or the mods you can make to any of them.
Here's a collection of tanks for your browsing pleasure.