I'm not an empty nester. But, there was 9 years of marriage before munchkin came along with just dh and I, then us and the dog.
Things I photographed then:
Outings, sky, mountains, nature in general, kitchen creations, around the house, friends, atmosphere (Christmas tree lights with my book open to read by it, candle burning on the bathroom sink, etc), games we played, bowling, hobbies, the dog. I actually wish I'd done better at telling our story then. The trials of being full-time students and full-time employees. The enjoyment of sleeping in or going out without needing a babysitter. The things you take for granted b.k. (before kids).
Now, things like kitchen creations are fun to look at because I don't make some of them anymore, or I've developed a better recipe that we enjoy more, or whatever. Sometimes I see a photo and think - oh! I should make that again!
Around the house is fun because we've moved since then. I've been scanning lately, so this stuff is fresh in my mind. Seeing where I painted the ivy on our living room apartment walls to make it feel homey. The first time we bought a deep freezer. The first time I canned. Now, you may be in a forever home, but even forever homes change over time. I can see in photos of my grandparents house when they added the outdoor swing that we loved to lay on and watch the leaves, painted the barn after the family photos, moved the organ to make room for Grandma's for the blind tape player (It was big in those days! She would've loved Audible!). I can tell similar stories about my mother-in-law, my parents, my husband's grandma. Sometimes, it's the little things that change that I remember.
Nature photos still make me happy and if you saw my "camera roll" you'd see more nature photos when we go on a hike than photos with munchkin or DH and I.
Every person has a story that only they can tell. We can try to tell the story of those around us, but they are still supporting players. We don't know their innermost thoughts. If you are stuck, you could try one of those story books (I have one called The Story of a Lifetime) and see what photos and prompts you want to tell.