Okay, so I have quite a few villager pics. But that was because of Easter and getting the question right etc. So other than Easter, how to you get villager pics?
Befriending a villager to a high level. The fastest way to do this is to fulfil their favours--since I don't like giving them stupid fish or bugs for their house, I rely on delivery favours, fetch favours, fruit favours (this especially works well if you give them perfect foreign fruit). Sometimes they send you a pic when they move out, as well.
perfect fruits, refurbished furniture, and if they ask for general bugs or fish, giving them a rare one. basically also never turning them down for favours.
The easiest method is with a town on the day of April 1. You play Blanca's game. You do a "Save and Continue" immediately after each correct guess (and villager picture received) before going to the next villager's house.
The other method is with a strong bond with an individual villager. That's achieved by doing everything a villager wants. I was told, about a couple months after I joined this site, that giving a shark, whenever a villager asked for an ocean fish, is an example of really getting into the good graces of a villager. That gestures like that will lead to a villager giving you his/her pic.