Some controls about flashing are already in the latest SVN code. You can either get one of the installers from here http://www.igniterealtime.org/community/docs/DOC-1822 or build your own version. Source is available via SVN http://www.igniterealtime.org/downloads/source.jsp But newest code main contain some bugs, i suggest turning native look and feel on, because chat window often just doesn’t show up upon new messages.
“Temporary option makes Spark to make ~5 quick double flashes and then it doesnt do anything. I think this can be changed to 3 normal flashes as it does in the Continuous option and then taskbar window should stay glowing (not just active) so the user will distinguish it quickly between the other windows.”