Add monochrome systray (status) icons
Subj, as that done in pidgin and others. The problem is when you want to create your own iconset, some icons not looking good in tray or some tray icons not so good for statuses.
The solution is to create overriding icons (i.e. tray_online.png) and if there's existing overriding icon, let the gajim put it in the tray. If not, place there status icon.