Silly ICE tricks: randomizing the primitive particle shapes

The primitive shapes (Point, Segment, Disc, Rectangle, and so on) are controlled by the Shape parameter, which is an integer parameter with 10 possible values. So you could just plug a Random Value node into the Shape port, set the mean to Box, and the variance to 4 or 5. Note that if the random value goes out of range, you get a point.

If you don’t want points or segments (or some other shape), you could just use a Randomized Value node to drive a Select Case node: