never tried ice...just ww and water.
it won't make your bike run any cooler though, it will just cool it faster when you start going.
you can try running without the thermostat if you want it to run cooler, but at higher temps, won't really matter since the t-stat opens at like 180...so once the bike gets up that hot, it'll be the same with our without the t-stat.

best thing you can do is to make sure your cooling system is up to par by flushing it regularly to make sure the hoses aren't plugged, deposits come out. also make sure your radiator fins are good and remove bugs from it.

you can also try a bigger radiator, aftermarket of course, or if you have room, add a smaller second radiator.