So once you unlock Harv’s island and then pay the required number of bells to get the fortune teller Katrina to open up shop you can talk to her daily and get either your luck for the day or she can tell you how close you are with one villager of your choice. You can do either of these, or both daily. You can look it up online but she has different sets of dialogue that tells you how good of friends you are with whatever villager you choose that day. She will also give you the option to “bless” your friendship with that villager as long as you have 10,000 bells or more in your wallet. Not your savings account, but wallet. As far as photos, each villager will gift you their photo once you reached at least level 5 of friendship with them, though it is kinda rare. It’s taken weeks for me to get some, others happened the same day I reached level 5. It’s all luck. You can put the photos up in your house on the wall, floor or any surface. Or you can place them outside and I’ve seen some people use them as decor next to villager’s houses. It’s just a nice long term goal to help keep the game interesting.