That little box uses the “Trim” color from your “Look & feel” settings. You can get rid of it by setting your Trim color to the same as your background color:

http://www.xanga.com/CLAF/default.asp

Note: if you “hide” the box this way, you’ll notice that there’s still a blank space when there’s no profile pic. Xanga creates that space so all your comments will be lined up, whether your commenters have a profile pic or not.

If you want to hide *all* the profile pics next to comments on your site, check out this faq:

http://help.xanga.com/profile-cpicshide.htm