This is done with the Marquee Html Code, and can be placed in your signature or in your actual post. You don't even have to use the html link to do it.
The code is [marquee*] Your Text Here [/marquee*]
I have added the red astericks * in this example, because without them the code would be activated and it would appear as the example above instead of showing you how to use it. When you use it REMOVE the red astericks.
To make a graphic move, you can actually insert the graphic from your Photobucket Icon between the bracketed marquee on either side (where I show "Your Text Here", above, or you can go to Photobucket and copy the IMG Code and paste it between your bracketed marquees.