(I didn't know which category to put this in, but put this in Comics since I imagine more comic creators will reply. Other novelists are welcome, too.)
When I first started writing my novel 4 years ago, I just put images in certain chapters for fun. I didn't want to stress myself out with it since it was a more casual project for me at the time.
Now, I'm a little more concerned with audience building. You may've seen a couple months ago where I went back to the first section of my story and added pictures. I'm happy that I did it, but now I have a new problem: There's about 34-35 chapters that either don't have illustrations at all, or the ones they have are from up to 4 years ago.
Have you dealt with similar problems of your old content not matching your new content? What did you do?