My suggestions:
- Stickied thread in any section you desire
- Maybe an award that is hard to get (e.g @Philly own award)
- Maybe have a monthly competition as this would get people engaged and waiting for the next one.
- Have a member of the month every single month. This would mean the winner each month gets a MOTM award, thus you will have people working towards getting this award every month = more HQ posts and more posts in general.
- If you are going to give out upgrades, give out Power or Onyx, plenty of people paid a lot to get Power+ or Investors and anyone can get them these days.
- Maybe anyone who is Power+ or above could be a part of a monthly giveaway of Koins / $$$ - basically have different giveaways dependant on what your upgrade status is.
If I think of anything else I'll add to this.