Okay... then you're looking at a hand-drawn style. Particularly look at finished maps in Hand-drawn styles, including the Tolkein-styles. I would recommend you look heavily into Ramah's techniques. To get these things to look right, you will spend time doing this.

If you don't have a tablet, then you're looking to do this bit by bit with a complete set of coherent brushes. Building those brushes will take time hand-drawing them and then poking around the tutorials section for advice on converting images into GIMP Brushes or PS Brushes.

Short summary: Become one with the Tutorials and Mapping Elements sections.