In pidgin-2.5.0 there are some strange things with size of tray pictures. For example, let's see in /usr/local/share/pixmaps/pidgin/tray/22. Some of them have size 22x22, but others -- 24x24 So, if you receive message, neighbour icons will slightly move when pidgin icon is flashing. In pidgin-2.4.3 all pictures have size 22x22, and all is perfect.