Part was a gift from someone, some I earned thru buying with in-game bells and the rest I just saved up ^.^
Its completely random but I think it depends if the new villager is outside or not. If you talk to Blanca (on plaza) whilst new villager is inside, new villager will most likely be the first one. if they are outside, they may or may not be the last one.
I load my game on the time of 6am. I get the pics in this order: normal, jock, smug, lazy/peppy, snooty, cranky, uchi
And the reason why is because of the times they wake up. In terms of none/beautiful/wealthy ordinances:
Normal-6am
jock-7:30am
Smug-8:30am
lazy/peppy-9am
snooty-9:30am
Cranky-10am
uchi-11am
Or you can just look at the chimneys and lights to see if they are awake.. whoever is next will be awake no matter what and they just fall back to sleep after you get their pic.
The only downside is you will always be getting everyone's pic every time..new villager may be first depending on their personality type.