Well, I have upgraded my laptop from Xubuntu 8.04.1 LTS to Ubuntu 8.10.
You may have saw on YouTube, there are more then just a cube.
But, how do I get it?
There isn't a plug-in for it?
We will learn you more about it.

Go to System -> Settings -> CompizConfig Settings Manager.

Go to Cube Reflection and Deformation.

Go to the Deformation tab and choose in Deformation your thing.
Note that "None" is a Cube.

Here you have "None".

Here you have "Cylinder".

And here you have "Sphere".
Ingore the glitched up screenshots, this doesn't happen in realtime.

Here you are!
I personally like the cube the best, it's not as huge as the other 2.
Pick your style! :-)