Well, the "3D effect" you're talking about is done with images. If you take a look at the blue header and footer of each post, you'll see that those are images and not just colored backgrounds.
There's several threads here on vBT that talk about how to add images to various parts of your forum. Most are done in Forum Categories and Postbit. Just do a search and I'm sure you'll find them.
However, it all comes back to your graphical skills as to what can be done.