The background tiles for the minimaps are stored in the client/res/maps/minimaps folder. For each Zone (.luz) file there is one folder. Each of these folders contains three zoom levels:

$ ls

Level 2 has the highest resolution, level 0 the lowest. Each of those folders contains multiple 256x256 pixel tiles that make up the map when stiched together.

Manual Stitching

You can use ImageMagick with the following command to stitch a single map. W and H need to be replaced by the number of tiles per row and column respectively. Usually that’s the square root of the total number of tiles as all known maps are square.:

$ montage -tile WxH -mode concatenate image_*.dds image.png