Since the pack already contains very similiar icons, I wanted to suggest adding the following versions:
Swipe vertically: Would be a combination of gesture-swipe-up + gesture-swipe-down (should have a vertical arrow with points on both ends)


Swipe horizontally: Would be a combination of gesture-swipe-left + gesture-swipe-right (should have a horizontal arrow with points on both ends)


Swipe vertically - two finger variant:
Same as vertically but with the gesture-two-tap hand as base.

Swipe horizontally - two finger variant:
Same as two-tap vertical swipe, only with accordingly rotated arrow.
Pinch fingers
Could take the gesture-tap as base and add the circles around the index finger & thumb and add icons to depict finger movement together.

Something similiar to this:

Spread fingers
Similiar to pinch, only arrows in opposite direction.
The first 4 gesture-swipe-<direction> icons exist already.
Seems I didn't express my intent clearly enough.
I referenced the existing icons because I need a combination that shows swiping in both directions (i.e. the icons should have an arrow pointing in both directions similiar to:
).
You have to remember that you are working with a 24x24 max size and it starts to get really difficult designing a recognizable hand and gestures at that size.
It should be possible to combine the arrows in the first four.
I thought he wanted pinching and spreading gestures?
@MrGrigri I wanted both the bi-directional swiping icons that @GreenTurtwig has just kindly provided AND pinching and spreading icons.
Rotating gesture-tap by 30 degrees or so (some angle which works with pixel grid) and adding the circle to the thumb is a good idea for pinch gestures. Could try fit in a diagonal dual arrow in one of the corners too.
Looks pretty good, but maybe rotate the arrows to 45 degrees? Might be a bit more clear that way.
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gesture-swipe.zip ?