I’ve often thought about creating a non-FTL space setting. The speed of light is the law. Traveling across the gulfs of space between the stars can take years to millennia.
For example, the PC’s can save a fledgling space colony, travel around the galaxy in hypersleep, to return centuries later to find the colony they saved is now a metropolis. Will the PC’s be remembered? How will their decisions have echoed across that time to shape the society?
Can the theme of deep space and eons of time work for a campaign? How could it be run?