I wouldn't unbalance the fan with the packs on the blades. But you *could* use the light mounting point on the bottom of the unit to put the basket on holding the ice packs, if you're determined to try the idea. Then at least you won't wear out the bearings or potentially break the fan mount at the cieling and have it fall on you (depending on how badly out of balance and if it's properly installed or not).
The efficiency thing still takes effect, in that it will put in extra heat into the house to re-cool those packs, that your main AC unit will then both spread out into the rest of the house (including your room), and have to try to pump out of the house (which if it's already undersized won't help it any).
You'd be better off to
1-- get a window unit; I have found them at goodwill sometimes, which is where I got the one I'm using now for less than $40, and it works perfectly.
2-- Add shade to the sunlit walls of the house, so the sun doesn't directly strike them.
3-- Add shade to the main AC unit, so it doesn't have to also deal with the heat from that.
4-- Cool the ground (or roof) around the AC unit while it's operating, so the air passing thru it is cooler, making a larger heat differential, and making it work better. If it's on the ground you could simply add a misting system around it so the ground is kept a little wetter, and so that when it's running it pulls the damper air thru it's heat transfer coils, helping htem cool faster than with just the normal dry air. If it's on the roof you could still use the mister, but I don't know what long-term effect it will have on the roof itself, and the water would be wasted other than it's cooling effect on the roof itself and on hte AC unit. At least on the ground it would also be watering the plants/etc around the unit, helping to grow shade for it if you plant the right things near it.
5-- insulate the outer (and/or inner) walls of the house, or at the very least your room. metallized foamboard isn't that expensive, if you just wanna put it inside the room where it won't uglify the house. You'd wanna put it on the cieling as well as the walls, in that case.
6-- insulate the attic of hte house. If nothing else, add another layer of whatever is already there.
7-- If you don't have double (or triple/etc) pane windows in the house, you can block them off with that metalized foamboard, or at the very least hang puffy quilted blankets over them on the window side of hte curtains, to hlep prevent heat from so easily getting into the room(s).
8-- close off vents in the rooms of the house that aren't used much, and close their doors too. Let the bathroom get hotter; you're not in there long enough to worry about most of the time, and if bathing or showering you're making the room hot anyway, probably. Plus then the AC doesn't have to deal with cooling that heated/wetted air, too. Any other rooms that can be closed off that aren't used much would help, too. The less the main unit has to cool, the better it will work.
9-- Set the temperature lower at night so the house in general gets cooled off better while the main unit works better becuase of the bigger heat differential, before day starts making it hotter outside, when it doesnt' work as well. Works especially well in the wee hours not too long before dawn.
There's other tips and tricks like taht scattered in my house fire thread and crazybike2 thread, and probably dayglo avenger thread too.