A standard here would be very welcome, though I still haven't seen anything I'd call intuitive. Visually distinguishing tap, double-tap, and "long press" is pretty difficult.
The Cue icons will be clearer at small point sizes, but if you have enough pixels the (mostly) graceful hands in the Open Exhibits library feel more appealing than Cue's big fingernail.
The Open Exhibits Gesture Library is another option. It looks like they broke the old link at http://openexhibits.org/gesturelibrary but you can see an example gesture at http://openexhibits.org/support/gestures/35/two-finger-scale and click around for the rest.
The Cue icons will be clearer at small point sizes, but if you have enough pixels the (mostly) graceful hands in the Open Exhibits library feel more appealing than Cue's big fingernail.