These posters are 180dpi for better print quality without excessive file size. I always use Inkscape to design them, often with the help of a good google image search for woodcuts and other medieval imagery.
And while we're here, let me take this opportunity to remind you to enter the TFH annual Terrain Compometition, which ends in a mere ten days! And what can you make in a mere ten days, I hear you cry? Well, why not have a mosey through the blog and find some ideas.