One of the games that I play is a turn-based strategy called Battle for Wesnoth. It's a free game (GPL'd) and it comes with a map editor. I found this to be a superior way to make maps for my storyboarding. I've yet to find a good way to convert it to an image file... I'll get back to you with the results.
UPDATE: figured it out (I'm dumb, there was a map screenshot hotkey).
UPDATE: I forgot that the textures are GPL'd as well... can't post it here
Grab it from here: