That a very old topic. i know.
Some fan made a D2 Map Randomizer. Actually it released a long ago by now. Some very good improvments are made t this and nw it true RMG and not just randomiser of existed maps (like first version). But that made from another ецщ guys.
Now you can combine it with RMG that build-in in D2 Editor and make a good random maps.
here simple randomizer (first one)
http://d2ext.sklabs.ru/download.php?id=files/D2MapRandomizer.zip (one of the mirrors, u can find it on google - only russian sites)
here imroved (second one) - video on YT:
http://www.youtube.com/watch?v=UBw626bU5J4 with download link to Google Drive in description
Again, only russian sites. Russian video.
First program is one-click (Перегенирировать\ReGenerate). Second one a bit larger but have a ENG interface.
Simple randomizer useful to quikly place Garrisons to neutral cities (what build-in RMG not doings) replacing it from neytrals stack parties.
Regenerator use some multipliers presets. And generate units using game data files - so it use every content in the game. not just created by RMG.