Check out http://meta.stackoverflow.com/q/107246/189958

Pertinent answer quoted below...


> Short answer: you can ask for anything you want, as long as it doesn't
> interfere with functionality.
> 
> Each graduating site gets its own unique design theme created by Stack
> Exchange's professional in-house design team (currently Jin), working
> with other designers as needed.
> 
> So far, every site's theme has included
> 
> - a custom logo and favicon custom decorative graphics (or intentional
> lack thereof) 
> - a consistent color scheme 

>Most sites have also received
> 
> - unique fonts consistent with the site theme 
> - decorative boxes and borders consistent with the site theme 
> - themed badge shapes/sizes/colors (color referring to background color, not bronze/silver/gold) 
> - themed tag shapes/sizes/colors 
> - unique upvote/downvote/favorite button images 

>Some sites have other changes
> that have to do with their topics. Photography's top bar is organized
> differently to make room for a "featured photo." Unix and Linux has
> slashes prepended to the text of its header buttons to give the feel
> that those link to "subdirectories" of the site. And Apple's <kbd>
> markup looks like an Apple keyboard's key.