Old school hand drawn map in photoshop.

[Chip]

Do you think it'd be possible to make a map like this in GIMP? Or is the free software not good enough? Because I'd love to be able to make maps that look similar to this.

[Freodin]

You can do with GIMP just about everything you can do with Photoshop. It is only the workflow that is different... quite often very different.
The main difference: PS allows you do modify a base layer with all kind of style layers, without destorying the original. In GIMP, most functions do directly change this base layer.