How to Get Custom Maps or Make My Own?

I currently play on an iPhone, and yes, I know that I can’t download maps to world box (unless there is a way) but I would really like to have a world map as one of my worlds, I was wondering if there was a way to either get a custom map someone or have a app that can help me make one? I am not a great artist and would mess it up on my own but I was wondering what map makers use.