The Wave
This is when people constantly do the wave... meaning, they undulate in your vision. This would seem that you had a little bit too much of the bubbly. Tipsy much?

Smoke
Well, this is actually a bit conditional. This would either mean there is fire... oorrr... someone's been smoking the "Devil's Lettuce." No to drugs. As for fire... duh?

Pervs (for the ladies)
Uhhh... self-explanatory?

Time-bombs
Ah yes... the time-bombs. Some people just can't hold their booze. Watch out for people who're about to blow chunks. You need not know what they had for lunch.

Cops
And finally we have cops. Party + Cops = Not Good. The fact that they're there means something's going on. Better hit the joint. (pun from 2nd sign, not intended)