In terms of visual FX: supporting animations would be cool. I watched a few videos at the Klooge website and while it's cool they support animations and can do things like aim and shoot fire from attacker to defender, the process was let down by an average looking GIF and some clunky animations sending the fire GIF from point A to B.
Otherwise I'm not really certain what is standard and what is not?
Playing to your strengths I think enhancements to the multimedia aspects and increasing the immersive nature of the game rather than say catering to specific rule sets. Adjusting graphics on the fly is useful and maybe you can have some preset filters like "winter", "summer", "day", "night" etc? If you can support animations including both visual and sound FX like "rain", "snow", "wind" etc would be cool too (I could see something like this being sold as an add-on perhaps?).
Aside from just sharing map and token visuals and rolling dice, I think Fog of War and other area of affect visuals are the single most important functions. Enhancements to these will always be well received. Because light shouldn't be able to pierce through walls I was thinking it would be nice if a GM could paint down mulple and independant solid black overlays (perhaps using something similar to the AoE overlays?). This way if a sealed room should not yet be revealed, the light source won't penetrate the the additional overlay until the GM is ready to remove it.
Anyhoo, I'm sure we've all had enough of me for now...
