[TYPO3] Wrap content elemts as determined by content writer

[Lucas Birk]

Hello,

I have a small problem with content classes.
I need to set a different background color, padding etc to different 
content elements depending on what they are as determined by a human.
In other words: If the content is an image of a cow make the background 
of the div green. If it's a fish, make it blue.
This decision should be determined by the person entering the content 
via a selector box because, as far as I am aware, TYPO3 doesn't know the 
difference between a cow and fish. They are both just images.
I am stuck with this line of code: renderObj.stdWrap.wrap = <div 
class="{$variable}">|</div>
Is it possible to throw a "real" variable in there some how or is my 
line of thinking wrong?
Thanks,
Lucas Birk.