With the proper planning, it would be relatively easy to design a house in such a manner that the climate could be naturally controlled. (relevantmagazine.com)
From what I've understood, the other person would be able to see how you've designed the house of the animal on the card. (animalcrossingworld.com)
They are typically unlocked by designing a house for the corresponding character, though some pictures can come in sets even if the depicted villagers don't live together. (nookipedia.com)