Actually, it's turned out to be a problem CC file after all. Sort of. I started my game back up, and the photos were there. Then I looked at the lot bin to see if the problem with the lots not showing up had been fixed. It hadn't, and when I went to look at my pictures again, they were gone.
So the CC file was making the lots not work properly, which was making my pictures disappear every time I looked at the lot bin, I guess. So it's just a matter of finding the file. :\

Thanks for the help anyway! You guys can lock this thread or whatever you do here now.

This is gonna be a little long, probably.
I have Uni, NL, OFB, and Seasons. My OS is 10.4.9... uh... I don't know what else would be helpful, so if you want to know anything else as far as specs, ask and I'll look.

My main issue is that none of my photos for one of my neighborhoods (maybe both, actually, I haven't checked the other) are showing up in-game. They're all still in the Storytelling folder for that neighborhood, they just don't show up in-game. Since I'm in the middle of a Legacy that I'm writing a story for, this has me a little (lot) freaked out. I haven't tried loading the game without CC yet, because I didn't think that could affect photos, but I'll probably try that tomorrow.

Now for the other issues I've been having that might have triggered this. I've been having trouble with the game crashing while loading a neighborhood, and sims (character files, to be precise) disappearing in that process. I constantly back up my neighborhood, so usually I can restore it without much trouble. I -think- this has to do with the file limit thing that's been talked about lately, but I'm not completely sure.
Anyway, this happened -again- just before I realized that all my picture were gone - but I think that the pictures were gone before this happened the latest time and I just hadn't realized it. (I was looking at the pictures in Neighborhood view, before this, and they weren't showing up then, and I just thought it was cos I was in Neighborhood view.)

The other problem I've been having seems to be sparked by various CC files. It makes my lots disappear - that is, they show up in the lot bin and all the already existing lots are still there, but if I try to place a lot from the bin, it shows up as an empty lot and if I try to build a new lot or change an existing one, the changes don't save. I can't quite figure out what causes this, but it's something in my CC folder (because when I take it out it goes back to normal.)

Uh, so, that's my litany of thing that are screwy with my game. Can anyone contribute advice, other than "delete your CC, reinstall, and get a better computer"?