None of the builds pictured are bad by any means, but there also isn't a whole lot that stands out about them either. I'd try to get more builds under your belt but on top of that I'd also try and up the scale of your builds as well too to appear more grand.
Thanks for applying, hope to see you update this app
I'll say it, but there isn't a special design I have seen here. They look a little bland, so depending on what you like building, I would work on some form of architecture for builds, maybe make them a tad bit more grand and large, vary materials to make them look good together, maybe background work for some parkour, familiarize yourself with worldedit, because that is a tool you will be using a lot, and maybe work on the arena thing. I can't say for certain that will get you the position, but it will sure as hell make getting it a lot easier