Accepting map submissions.

Well, there are definitely maps like that.
And if there aren't, you can basically modify any map.
All you need to do is open it in the editor, place 1,000 demons, and use a script to set the victory condition to be their destruction.
If you don't have that much knowledge of scripting, you can create any victory condition with a few mouse clicks (after studying the editor manuals a bit, if you really can't figure it out).
For example, accumulate 1 million gold, build a Grail, gather troops, destroy a hero, annihilate an army, capture a castle, or level up to a certain level.

So, grab the editor, find maps on map sites, and go for it – create the map of your dreams (based on someone else's map :D).