Do a series of a dozen portraits of only elderly people. Keep the composition the same for all portraits and no smiling subjects. Try to also keep your lighting the same for all shots.
Insisting that your subjects not smile will give an interesting tone to the series of portraits and having to convince twelve elderly people to do it will improve your photog to subject skills.
You'll be surprised what you learn and it may inspire a different project.
You can check out some of my work here. Just a small selection of old work but you might find something there that interests you.