I'm pretty certain that he used kgpanels for the backgrounds, not Pitbull. Textures should be included in the package you linked. Those rounded corners are textures, too.
As for oUF, take a look at other layouts and how they implement textures. There's an extra sub forum for oUF where you can get help. But keep in mind, that it's a good idea to already have something (code) to show/work with to get some/better/faster help. Instead of just asking "how to xyz". As this can be figured out on your own with some research and that's work to be done on your part if you really want to get somewhere.
