I don't think you can do that... but what I did was find a bunch of scripts where I could change my name on my site.
so, instead of being thenocturnalmercenary, I changed it all to x_LoNeLy_bLuE_x.
if you want to see it... http://www.xanga.com/TheNocturnalMercenary
^-^ I even changed it on a few of my friend's sites. My screenname is still TheNocturnalMercenary, but at least on my site, it shows up as x_LoNeLy_bLuE_x!