It could look like pretty much anything, even The Matrix (as shown here), it all depends on the owner. The look and feel of the hacked iPhone and iPod touch interface is completely customizable, not to mention you can install any combination of 3rd party apps on it which are all available through the latest Installer.app. Take a peak at what current users are doing with their hacked devices at this great Flickr pool of hacked iPhone screenshots.
There are hundreds to click through, so if you have a Flash-enabled browser we recommend viewing the slideshow. This way you can kick back with some pretzels and beer while you contemplate taking the red pill, or the blue pill.