OP is edited, but here are the May categories anyway...
A film with the number 5 (Five, Fifth, etc.) in its title (not a sequel):
A film with a title that starts with the letters I or J:
A film from the current IMDb 250 whose ranking includes the #5 (i.e. 15, 25, 54): (see list
here)
A film from the 1940s:
A fantasy film:
A film with an animal in its title:
A film mostly set in space
(Space Day, first Friday of May):
A film based on a comic book
(Comic Book Day, May 4):
A film with prominent Muslim characters
(Ramadan, starts May 5):
A film from Mexico
(Cinco de Mayo):
A film from Orson Welles
(born May 6):
A film prominently featuring mothers
(Mother's Day, May 12):
A film that won either the Palme d'Or or the Grand Prix at Cannes
(May 14-25):
A film set in a museum or featuring them prominently
(Int'l Museum Day, May 18):
A war film
(Memorial Day, May 27):
I might go on an MCU mini-binge; I had planned to watch several of their films anyway as "freebies", just to see if I could catch up with everyone. Lucky for me, many of the categories I had already come up with line up with the MCU films I need to see (space = GotG Vol. 2, IMDb ranking = Infinity War, fantasy = Thor: Ragnarok?, War film = Civil War, Infinity War, etc.) If anything, I only tweaked one or two categories to suit my needs
(added the animal title, and didn't know there was a Comic Book Day), but what the hell, it's my party.
As usual, recs are welcome.