Seeing how the Apiary now relieves unrest across your Kingdom, it occurred to me that the game could really benefit from even more unusual resources, as a way to make particular areas of the map matter.  Some could benefit the entire kingdom, some the one city, and some could benefit the city only if it were of the right type (conclave, etc.).  Furthermore, some could be revealed only by circumstances (the old technological prerequisite, but also maybe as the reward for a quest, a map showing the location of a resource... or as the reward for winning some battle, or taking over some lair).

With all the attributes and resistances in the game, the possibilities are endless -- which could make for a highly varied list, only a few of which showed up in any given game.