There are plenty of minor Gods, to many to count.
Loads of them, hundreds of minor Gods, because after all they count Daemon Princes as almsot gods themselves, the step up is a demi-god of Chaos.
The books mention loads of gods but four main Chaos Powers: Khorne, Nurgle, Slaanesh, and Tzeentch.
Although not many are named, if any at all, I guess if any of the Primarchs survived they would be gods, and I guess there will be something somewhere that lets you create your own god for use in a game (with the opponents consent, which generally they aren't gonna let you use a god.) but the reason GW don't publish much on them is this:
Imagine the scene. Two gamers, one of Chaos, one of Space marines, are about to start. The Chaos player asks:
"Oh, you won't really mind, but I just thought I might use my God for this match."
"You mean Daemon Prince or some special character?" replies the Marine player.
"No no, its the god of KILLY EVERYTHING and he was stats 10 all the way across, except he has 20 wounds, he instant deaths everything on a 2+, hits automatically, re-rolls failed wounds etc etc..." the Vhaos player rambles on.
"And guess what? He's *only* 150pts!"
The Marine player begins to pack up, before sarcastically remarking,
"You wanna use Horus too? Or shall I get out the Emperor, I just happen to have a couple of them, you wouldn't mind if I used two?"
When the Chaos player eagerly says yes, the Marine player shouts *Purge the Unclean* bomps him on the head and runs away.
A bit over the top but that's what GW does it for. (Or rather, doesn't do it.)
Give a man a match, and he's warm for a day.
Set a man on fire, and he's warm for the rest of his life!