Iceblock with a pet out is a good standard offensive move...
You CAN still do one important thing while you are iceblocked... (besides "get healed by someone") which is cancel iceblock at any moment you wish up to the point where it expires. Which means you can do things like blink away at an unexpected time, pop out of the block to suddenly cast counterspell on a pyroblast being cast at an arena team member, pop out to suddenly frost nova/blink because they stupidly clustered around you waiting for the time to be used up.
Alot of other uses have been covered, falls, cooldowns, getting healed... infact it is probably the best way to signal the healer... "hey, your mage is about to die over here" is to pop iceblock... its a good visual clue that they need to toss a heal your way... and if they want they can even toss a heal-over time effect since they are cheaper instead of a big monster instant.
The comedy use hasn't been covered yet except for the neat effect of throwing aggro off you onto an attacker if you are being attacked.... You can do silly things like save the entire party from a wipe by getting aggro (if you can... and running off in the opposite direction of the instance entry... run run, blink... face the boss, iceblock.... soon as he gets to you... he chases party... (they are already running out of instance... (except for your dead healer... or whatever is gonna cause the wipe..)) so they have covered alot of ground... let boss go a ways... cancel iceblock... he turns and runs back to you.... just blink past him...... then invis or just runout with blinks or even die... at least you saved the rest of the group a crapload of repair bills. The aggro loss and regain ability of iceblock can actually be useful sometime and not just a "delaying" tactic. It can buy the rest of the group time to flee.
In PVP it forces the enemy to waste time, and shots.. It wastes a hunter's pets time attacking an invincible target... (till he notices) If you Iceblock at a flag they can't start capping/recapping a flag because you will uniceblock before they are finished and wack them to stop the cap... You can iceblock at the enemy flagstand in WSG if a huntertrap pops so you wait out the slow effect before grabbing flag.... (NOTE: If you iceblock while carrying a flag you drop it.)
All kinds of inventive uses... using it to cluster enemies into a tiny knot around you if you are AOE grinding.. (nova, blink, jumpspin, aoe is standard coming out of an iceblock)
Its a good spell.. you firemagi will like.