A display issue I noticed right away - buddies who have a long away message set cause the client to display it all, making a huge horizontally scrollable area and pushing the minimize/maximize icons off screen. I would think an enhancement would be to only display what you can without giving a horizontal scrollbar. If a user hovers the mouse over, display a tooltip with the message.
Also, it looks like Java is the back end language. I assume you’‘re using the Smack libraries for talking to the Jabber server. I wrote some plug-ins for Smack to handle IQ-based Avatars and VCard avatars, would you like them? The basically store a String containing a Base-64 encoded file along with the mimetype (which isn’'t guaranteed to be correct). With a bit of modification (setting max filesize, ensuring JEP compliance) perhaps they could be included in future Smack distributions?