Congratulations on paying your credit card off!
Having additional lines of credit open is fine. If any of these cards are actually store credit cards that can't be used except in store, cancel them. Having store credit can hurt you.
Otherwise, leave them open for now, until you get your pre-approved mortgage, as sometimes closing them can hurt you.
As well, one of the more interesting aspects of credit cards is that there are service charges you can actually opt out of. Research your charges to see if this applies to you.
If you are going through a mortgage broker outside of a bank, and the issue comes up that you have credit cards with zero balance, and they have an issue with that, and you have no concern with cancelling the cards, tell them, and offer to cut up the cards on the spot, since it is a non issue. That should close any concern anyone has.
Best of luck and happy home hunting!