- Step 1: Create a minimap image. Turn off all waypoints, tags, etc. and to view the entire map from the top and take a screenshot of it.
Step 2: In an image editing program which supports tga files (such as photoshop) load the screenshot. Crop the image and resize it so that it is 256x256 pixels. (Note: If you're using photoshop I'd suggest you quickly using the "auto levels" and "sharpen" tools, they are quick and easy ways to make the image look much better)
Step 3: Save the image as yourmapname_art.tga (make sure its 24 bit) in your map's folder. The "_art" section is important, otherwise it will only show up in the map selection area, not on the minimap.
And you're done!