desktop imgs

[Cara Quinn]

  Hey All, might any of you know where I might find the setting for  
the way a picture will be displayed on the desktop?...

I'm familiar with the desktop / screen saver pages in system prefs and  
can change my pic, but I have a pic of Serenity from FireFly which I'd  
like as my desktop however, it wants to tile instead of be centered,  
so I'm wondering where I might fix this?...

Thanks so much and have an awesome evening!...

Smiles,

Cara  :)