for me the tray icon (using Windows) is not removed when I exit Spark (using the TNA popup menu and there “Exit”). It will be removed as soon as I move the mouse cursor over the icon but this is not the normal / right behavior.
Sometimes (nearly every time) I have a black border around the Spark icon. And it looks both in the TNA and in the task bar like there are some pixels missing on the left. It seems that this is caused by the design of the icon with 5 pixels on the left which do not make a good rounded shape. It looks like a flame where one did chop of a bit.
I guess that you did resize the image http://www.igniterealtime.org/fans/logo-spark.png without adding a left border before doing so. This looks really bad. So if one could add a left border and resize it again I would be much more happy.