I'd suggest to add more pairs, maybe even more than only traditional ones. The ability to trade a coin for many others directly, not only via btc/eth/ltc/dash will certainly get you more customers once you establish yourself.
We so far have added 4 more currencies since launch and are on the lookout for more. If you have any suggestions let us know!
I said pairs, not currencies. Say, you want to trade your ONION straight to LTC or SIGT, etc.