The house of the mouse is always a must, even if there's not much prop related there. They used to have some Marvel stuff until they shut down Innovations, now the only prop/costume related stuff are a few costumes at CA Adventure from one of their shows, I forget which one but it's sort of fantasy related is all I can remember.
If you're a big Trek buff, there's always Vasquez Rocks, it's out of the way and not really in LA (truth be told, not much of what gets called LA is really in LA proper), but it is a very iconic locale. Just make sure you pack good shoes and light clothes along with plenty of water, it's hot out here and it's Vasquez Rocks is not exactly a paved tourist attraction,
As far as BTTF goes, one place you can visit is the stand in for the Twin/Lone Pine(s) mall, it's the Puente Hills Mall located in the City of Industry. It's a decent mall, nothing fancy there's not a whole lot else to see in City of Industry but around the mall and in nearby Rowland Heights, and Diamond Bar there's lots of good Chinese and Korean food to be had., especially Chinese food.