Since revision 967 htmltextview has this kewl feature:

To test it, you have to enable the /eval plugin and type in this:
/eval import gtk
pixbuf = gtk.gdk.pixbuf_new_from_file(”/path/to/image.jpg”)
conversation.ui.textview.set_background(pixbuf)
..And what does this mean? Background sharing support! And no, don’t think that we were losing our time with this. The idea was to add background image support with CSS styles in htmltextview, to be a step nearer to adium styles :D.
We have been working in this for weeks, without getting “decent” solutions. [technical]The ScrolledWindow was scrolling the background too, in an ugly way[/technical]. We’ve tried lots of things, even asked the pygtk mailing list — without getting replies of course. (TODO: reply to myself with the solution)
One day, alencool read that mail, tried to find the solution with cairo, and came up with a cool transparent window+textview that requires compiz. The problem was that we had to make all the window transparent to get it working, something quite impossible. But he introduced a new idea, [technical]connecting the ScrolledWindow expose-event to the child htmltextview queue_draw[/technical]. Yesterday I tried it with one of my old solutions, and surprise, it worked fine.
“Background sharing” is “a protocol feature that extends file transfer to send images and set them automatically as backgrounds”. That means that WLM can share the background you choose for the window with your contacts. Pretty stupid feature, but people like it.
This is just the first step, and the hardest one (because we thought it was impossible). Now roger should update his FTContext to identify better background sharing file transfers, and someone else code the GUI part (an icon in the toolbar).
And yes, we can add background images to the user list too. Who said that qt is better?