I've just finished a very rough draft of a tutorial on making isometric wall graphics, and have put it up for viewing on my website. You can check it out here, or it can be viewed from the Technical page on the site. The tutorial includes a link to a sample .blend file I commonly use as a template when starting a new wallset, with a camera oriented on a stage and set to the proper isometric perspective to fit the 2:1 tile ratio of the game engine.

It's pretty rough, but it covers the basics of how I used Blender and the Gimp to create the wall graphics for 2D Golem, ensuring that they tile seamlessly. This is only part one; I would like to go a little bit into how I do man-made-type walls, doorways and arches, etc... in another tutorial, although the procedure is roughly the same idea.