NO! Perhaps you're thinking of OS X, which indeed supports icons of that size (and more- up to 128x128 in versions up to Tiger, I think, with subsequent versions pushing that up to 256x256 and eventually 512x512). Systems 7 through 9, on the other hand, only support icon sizes up to 32x32 pixels (and maybe 48x48 under some special circumstances, I'm not sure).
And OS 8.5 and later support 32-bit icons, so you can have icons with fancy transparency and translucency effects (which is irrelevant to 68k's, of course, because they don't run 8.5).
c