ohr-cartographer
ohr-cartographer is a command-line tool for rendering maps in .rpg files as .png files, written by Spencer Zhang. Each tile appears in full size 20x20.
While this utility still works as of Gorgonzola, it is no longer necessary because you can export map images from the map editor, in the Import/Export Tilemap submenu. The builtin method also lets you include NPCs. But one nice feature of ohr-cartographer is that it can export images of all maps at once.
Download from GitHub here. Click on "Clone or Download" at the top right and then "Download ZIP".
Windows users should run bin\mapper.exe. GNU/Linux, BSD and Mac OSX users should instead run from the commandline (follow the instructions on GitHub. You will need a copy of the unlump utility.)