Medieval (castles)
In that case, definitely not Neuschwanstein. :-)
If you can decipher a bit of German, try the sites mentioned here for early or later Middle Ages. Check if one of them is somewhere near your itinerary.
Art museums
Anything in particular or just any kind of art?
You should certainly find some in Berlin (Museumsinsel, again); Munich would also be a good place (Alte and Neue Pinakothek), but there are also some quite noteworthy places not anywhere near your itinerary (Sprengelmuseum Hannover, Kunsthalle Emden). Depends on what you are interested in.
street photography
Make sure you understand the laws on that which are quite different from most U.S. states. An attempt at a short summary:
- people only with their consent
- children only with their parents' consent (people have become quite sensitive about that)
- If you take a picture of a building and a person happens to be in it without being the main focus point, that's o.k. ("Beiwerk")
- Taking pictures of buildings etc. from public grounds like sidewalks is o.k. ("Panoramafreiheit"), don't need the consent of the owners. This does NOT include stepping up on a ladder or flying a drone etc.
Cycling
Does that mean for getting around in a city, or would you want to take a tour? There are classics like the Moselle valley of course, but a lot more. And you can rent bikes in most cities and get around by bike quite well (some cities more, some less).
Wine and beer tasting, German and local food
See my previous post.
ethnic, French or Italian inspired restaurants.
Italian + ethnic: all over the place. French, not so much.
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On your previous wishlist, you had the word "nature". That seems to have disappeared now. Is it just the lack of time, or is it not that far up on your list of priorities?
Depending on your priorities, you might make that one full day in Dresden and add time (at least half a day) for the Elbsandsteingebirge. That would be some beautiful nature within easy reach of your itinerary.