Zooming a la Impression Publisher would be fun. A feasible option would be: Ctrl over window, drag away from centre to zoom in, towards centre to zoom out (ie: where you're clicking remains under the mouse, but gets bigger)
G0tai: having to hover over an icon is not intuitive, as you can't figure out what they do without interaction (intuitive: capable of knowing without deduction or reasoning).
RISC OS 2/3 icons no longer accurately describe their purpose as they used to (that cream box doesn't look like a HD, as it's representing an external HD in a case).
RISC OS 4 icons are near enough (they're a cross between the old style RO 3 iconset and the Phoebe iconset, so it's fairly obvious what everything is again as everyone's seen a tower case)
And if it bothers anyone that much, why not just stick your preferred iconset on a floppy with an obeyfile and take it with you?
FYI: I redesign icons from old proggies to make them fit in with RO4, and I add masks (grey boxes behind icons look naff with a blue iconbar)
I occasionally change theme, but I've got used to my self designed one, which I'll put up when I remember.
And the reason I first changed my icons? So people wouldn't instantly say "Eurgh" when I turned on my computer (o: