[DustyPorViva]

I say new. If anything, I would reuse an overworld of one of the many servers that have fallen into oblivion because it's one of the things I can't do on my own.
There are numerous problems when you reuse old content... most of the time you have to redo it all anyways. On the far end of the spectrum, people redo it to the point it's not recognizable and just slap the old servers name on it hoping to garner attention of those who loved it.

If you're going to put that much effort into a server, why not simply make it your own?