I didn't necessarily notice things in my photos that I had never noticed before when I got home, but I learned things on the DIS here that I didn't previously pay much attention to, so then that drew my attention to other things when I went back to DLR:
Those weather vanes - like that Pirate ship - are up in several places around Fantasyland (maybe even in a couple of other spots in DL too? Can't recall). I had never looked up to notice them until a couple of years ago, when I noticed that people had posted photos here on the DIS!! So the weather vanes are a sort of overlooked hidden gem of DL.
When I actually began paying attention, I noticed many more fountains/statuettes and topiaries than I had realized existed before.
I had never paid attention to the horseshoe and hoof prints in the ground of Frontierland until a couple of years ago.
Also, I had never noticed all the different bathroom signs around DL and DCA until 2008 or so. Those are easy to ignore, but they are hidden gems too! About 75% of them seem to be themed to the specific land in which they are located or the attraction which they are near, so there are little bug people on the bathroom doors in A Bug's Land, or little aliens on the doors in Tomorrowland, etc. So cool - and the more I look for them, the more I spot!
And, of course, I love that all of the plants, bushes and trees around Tomorrowland are either vegetables, fruits or herbs of some kind. I had known they were there, but I hadn't quite realized how many different edible plants/bushes/trees there were around TL until I really began looking more closely. So there were far more veggies, fruits and herbs than I was ever aware of.
On our last DLR trip in December, while waiting to get on Mr. Toad's Wild Ride, my friend and I were pointing out all the different varieties of toads and frogs inside, in the queue area (not just on the walls, but in the bookcase and all over). We had never realized there were so many different ones.
I love that element of being able to go to DLR and always have that discovery or revelation where you say, "Wow! I didn't know that was there!"