I'm not sure how possible it would be, but how cool would it be if there was a different hazard sign for each of the classes?

The headshot one for Sniper's weapons

a fire hazard for Pyro's weapons

Explosive warnings for Soldier and Demo, or Demo could have some

Heavy could get that one sign where the hand is being crunched by gears (you know the one)

Engie could have a hard hat / construction zone warning

A bio-hazard sign for Scout because *schadenfreude.mp3*

Some kind of health warning for Medic, or maybe the biohazard would be better on medic, though the toxic scout player joke is hard to pass up

The electric warning could work for Spy, because the majority of his tools are very technology based

And multi-class items could just get something more generalized, or maybe a random one of the listed signs.

Though this is assuming something like that could be possible AND Eric Smith doesn't botch the implementation of it.