I disagree with what a lot of people have posted. It's not the story, advertisement or even a lack of content nowadays. It's the way the server is run.

The problems stems from the direction that you (and by extension the rest of the staff team) are moving in:
Every single idea you've come up with involves taking players away from other servers and we saw proof that this was the goal of the zone staff team during the Christmas Event. Stop looking to other servers in order to find the growth you want. If you continue to try to please players by giving them what they already have on another server, you lose any and all shreds of personality the server had. If you want the server to grow, you have to begin to attract a player base that want something different than they get on Classic or Era. You have to look away from what already has been successful and actually try something new. It sounds harsh, but as someone who doesn't play the game much, nothing released recently seems original at all. There is no reason for me to role play on zone instead of Classic. If I want to shoot guns, I'll log on era, because the gimmick of 360 shooting isn't a gamechanger.

The server has had so many opportunities to create a different type of game. But every time, there is zero innovation. You could have gone in the direction of PvE missions, and actually created ones that weren't ****. That would have been completely different than what is on the other servers. The planet system could have been great. Instead of being actual worlds to be fought over, they're just glorified towers. In fact, they're worse than towers, because they aren't even in the regular world. There is so much you could have done to distinguish Zone from every other iOS server, but instead you look at what is already popular and try to hop on the bandwagon to grab a few more players.

Focus on making an appealing, different game for new players then you can move on to the minutia like customs. Custom heads aren't the issue here. The issue is that there aren't enough Graal players to support 5 servers the size of classic or era. So, instead of trying to cannibalize the market by actively trying to take away players from other servers, actually make your own game.

The way it is now, Zone is a **** server, but it has a ton of potential. If you want to be great you have to play on your strengths. Don't just be era in space, use your setting to the full advantage. Don't take ideas from other servers, expand upon them and create your own. Originality is what peaks interest in people viewing the appstore, and I'm telling you now, as someone who looks at the game from the outside, zone has zero personality, it's boring. It might sound like I'm flaming, but its not a hidden fact that a lot of players dislike zone. I'm not going to beat around the bush. As it is, Zone is not appealing to me and, based on the player count, not appealing to a lot of other players.

TL;DR Make your own game. Don't copy another. Originality draws in players.

Edit: Also I understand that it's hard to find good staff (especially on a server that isn't one of the most popular) but you need to work on quality control. It's great that you have dedicated members of the staff team, but sometimes you have to tell them their work is not good enough. A lot of the graphics on zone are sub par and the levels are pretty hideous (although that might be the fault of the tileset, it's pretty ugly). Quality control is one of the biggest changes in Classic over the past 3 years. If you look at an older release like yorktown and compare it to newer content like the railways or MoD town, there's a huge difference. Never underestimate the effect of polish.