Looking good.
One thing concerns me: that the EM generated column icon rules will not be easily distinguishable from user created column icon rules - other than the fact that they use the entity_reserved.png icon. I wonder if chaley would be amenable to adding a 'hidden' flag on column icon and colour rules, and a show/hide hidden rules toggle on the L&F Colour and Icon rules dialogue tabs.
Aside: I don't much like the stylised 'e' as a column icon - too obtrusive. But I quite like the Entities Manager toolbar icon. So I will replace entity_reserved.png with a copy the of entities_manager.png -- unless you beat me to it
BR