I've made a mission that makes it rain chemlights. Set the settings to max:
http://sacha.ligthert.net/screenshots/ARMA/3/feedback/arma3%202013-03-06%2022-33-10-523.png
http://sacha.ligthert.net/screenshots/ARMA/3/feedback/arma3%202013-03-06%2022-33-06-706.png
I made it rain Chemlights, expecting a wondrous colourful wonderland. Instead I got little dots in the grass with lights popping up randomly.