General:
* Ideas
* Cogitations
* Conceptions
* Notions
* Reflections
* Meditations
* Musings
* Ponderings
* Imaginations
* Perceptions
More specific:
* Feelings: If you're talking about emotional thoughts, you could use "feelings," "emotions," or "sentiments."
* Beliefs: If you're talking about thoughts about what's true, you could use "beliefs," "opinions," or "convictions."
* Decisions: If you're talking about thoughts leading to choices, you could use "decisions," "judgments," or "conclusions."
* Dreams: If you're talking about thoughts during sleep, you could use "dreams," "nightmares," or "visions."
Informal:
* Brainwaves
* Ideas
* Stuff in your head
The best word to use depends on the specific context and the tone you want to convey.