As said in other posts, you need to create a symbolic link TO your /maps/thumb folder INSIDE your /data/maps folder. The two paths are below to make this easier:


The way I did this was by following This Tutorial[www.howtogeek.com] and using the graphical shell tool. Don't worry, it's not a virus. The link to download it is Here[schinagl.priv.at].
If you don't trust me you can do this with command prompt, but it's much more difficult.

Then, after you've installed the extension, you do the following steps in order:

1. Right click the "thumb" folder ITSELF (not inside the folder) in the first directory, /garrysmod/maps
2. Select "Pick link source" from the right click dropdown menu (this is the graphical link extension)
3. Then, right click WITHIN your /data/mapicons folder (the second directory)
4. Select "Drop As" and then "Symbolic Link" from the dropdown menus
5. Rename the newly created shortcut folder to "thumb" so that the icons save to that folder, and then get redirected to the proper directory.

And that's it! (I'm about to test it now, will edit if it doesn't work)

PS: to the mod author, the next time you create an incredibly useful mod, maybe include some basic instructions you lazy hack. This literally took me 30 minutes to do and write, and will probably save a lot of people the headache of having to piece through your sloppy comments.