You can also write about:

• a nostalgic topic to see if others remember the same thing
• some weird dream you had
• a philosophical view that you may or may not believe for yourself
• anger or some other visceral emotion (people love that)
• TIL (today I learned)
• something vague that you can only hint at and can't go into right now
• something you know nothing about but are good at faking experise
• the 100s of ideas you have but have no idea how to implement
• the one time an entire weaponized kitchen was thrown at you

I'm sure there's more.