Based on my exploits, a guide to "repartition" the N900: http://sumoudou.org/0/5.html BEWARE: if you mess up in any single step, you'll brick your N900, and will have to reflash, so not for the meek. You're on your own. But I did it this way, so it works.
cd /usr/share/ for FILE in fonts icons locale mime nokia-maps pixmaps sounds themes tutorial-applet zoneinfo do mv $FILE /home/root/usr/share/ ln -s /home/root/usr/share/$FILE /usr/share/ done