Think about what players are going to to when they reach max level and get all the equipment? Don't think they will just flood the PvP room, cause that will not happen. Most likely they will get bored and move on.
What are you going to do to sink the billions of zeny that are going to flood the economy? What will you do so that Zeny still has value even on a high rate?
If you think opening a new server with nothing original to it will bring you a successful server, think again. You need to find a way to bring people into the server and keep them there. Otherwise you will be stuck with a server with 10-20 online and close it within a few months. Downloading a bunch of pre-made scripts from rAthena and Hercules forums is not an aswer either...there are already hundreds of servers with those scripts.
Find a niche that is not being served and try to serve those players. You cant and wont please everyone so always stay true to your server's core niche.
Last and not least...Unless you are REALLY GOOD at scripting and can do minor modifications to source code, you probably should not try to open a server. The competition out there is fierce right now and the big servers usually have dedicated administrators that are capable of a lot of things. You will be directly competing against them so your skills should be able to match theirs.