I don't get the point of iPhone icons unless you're trying to make people be like "ooo, it's iPhone-like". But to each their own.

Anyway, people should stop telling everyone to replace the system-wide icons without explaining what you're telling them to do - or telling them that they have multiple choices in how to do it.

You can instead put them into /home/user/.local/share/icons/hicolor/<subfolder>

These will always get used by Maemo instead of the ones in /usr/share/icon/hicolor/<subfolder>, AND they will take precedence over whatever custom icons themes bring in.