No other options yet, if they were added, they would be added for some reason (implementing some new feature), and that new feature would be announced for sure

As for complete reference of existing maemo mplayer additional options, I may update maemo mplayer webpage and add this information there if I find some spare time for this. The original plan was to have a wiki page for documenting these options, but apparently garage wiki can be modified by developers only and that defeats the whole idea