I am definitely in complete support of this idea/concept. It shouldn't be that hard to implement. Each group of Images could have it's own (sub-)folder(s); one for each type of citizen. Then when a citizen becomes available: one portrait from each available type could be presented. Call them Candidates for office (or whatever suits your fancy).
Either that or simply get rid of the pictures altogether and just use the icons.
However, the pictures do add an extra dimension to the game. But, like Syrkres said: it's tough making a person that looks like a miner be Commander, etc.
Having the ability to choose the right person for the right position (based on their picture) would ease my OCD when it comes to such matters.
SK