How to make portal skin diferent than forum skin ?

[Monikita]

Hey, I was thinking, how to make the portal skin look diferent than forum skin ?
For example, here is a forum (http://beastistheb2st.my-goo.net/)
It's portal has diferent picture and skin.
Does anyone know how to make it ?
Or I need to create that kind of look with photoshop or other program ?

Thanks for your time