The process is identical to the one described in this thread, however all PC components need to be translated to the Mac equivalents:
http://forums.boredaussie.com/viewtopic.php?t=11890
Step 1) Editing the registry:
Well, Macs don't have a registry however they do have Preference files. To edit the Preference file for Warcraft you will need a Resource editor such as ResKnife. The best version to use is 0.63 b3 and I've attached it to my post because it's annoying to find/extract (ResKnife063b3.zip).
Next, in the Finder, from the Go menu, choose Go to folder. Type in ~/Library/Preferences and click Go. Find in the list "com.blizzard.WarcraftIII" and open it in ResKnife (you may need to do it twice as the program is a little buggy or drag it to the Dock icon). You should see what I have in the attached resknife1.png.
At this point, click create and create a new resource with the name:
"HKEY_CURRENT_USER\Software\Blizzard Entertainment\Warcraft III\Allow Local Files" (copy/paste this without quotes)
Add in a resource type of "HKEY" (again without quotes). It should look like resknife2.png. You can click create once this has been entered.
At the bottom of the resource list, should be the one just created. It has an ID of 128. Double click it to edit it.
In the Hex entry, type in "00 00 00 04 00 00 00 01" like resknife3.png, close and keep the changes to the resource.
You can now choose Save from the file menu to save the preference.
(on a side note, editing resources was much easier in Mac OS 9 with ResEdit. OS X is phasing their use out however a few older programs still have them for backwards compatibility)
Step 2) Extracting the backgrounds
There is just way too much involved in this part getting it to work on Mac OS X. You need an MPQ extractor - which is simple enough to find (I had most success with "Diablo II MPQ Tool (MacOS X)"). Due to the way MPQ files work, the programs must have a list of files contained in the archive before attempting to extract them. I did not find an MPQ program that had these already available or a program that allowed the listfiles to be added easily.
Instead of going through everything I did, I've uploaded the modified Diablo II MPQ Tool that I used. This version has had the revised Warcraft lists added into it using ResKnife. You can find it here (too big for an attachment to this post unfortunately)
Once the MPQ extractor is running, you need to find the background .mdx files you wish to use. They are typically located under ui/glues/singleplayer/race/*.mdx. The files are not listed in order (however are in some sort of groups) so it may take a while to find exactly what you're after. The Arthas one I posted earlier is located at UI\Glues\SinglePlayer\Undead3D_Exp\Undead3D_Exp.mdx in the war3x.mpq (it's an expansion campaign background - open war3.mpq for RoC backgrounds). Select the one you want and extract it (File->Extract and choose a location to put it for the time being).
Step 3) Adding it to Warcraft
Find your Warcraft folder and create a path like this
Warcraft III/UI/Glues/MainMenu/MainMenu3D_Exp (for the TFT background) or
Warcraft III/UI/Glues/MainMenu/MainMenu3D (for the RoC background)
If you are changing the TFT background rename your extracted .mdx file to MainMenu3D_Exp.mdx and put it in the MainMenu3D_Exp. RoC backgrounds go into the MainMenu3D folder and are called MainMenu3D.mdx. Use addtowar3.png as a reference.
Once this is done, it should be changed.
There are a few other items that can be changed on the background main menu such as fog and lighting, except I cannot remember which file it was in. If you want to research it, just extract the appropriate file, edit it, and add to to the Warcraft folder with the same structure.
There is also a RoC beta main menu background of a castle that is pretty impressive. I've attached it to this post as well (the fog is not quite right for it though and needs to be edited with the file I mentioned earlier).
hmm. Limit of 5 attachments some will be in the next post.
