Apologies if there's already an article on it, but what hitting it actually entail in game, if anything at all? I see maps like Atlantis that have a whopping 236 sprites placed on it, and it just made me curious if if was a map limitation, or something that would have gameplay ramifications.
It's just an artificial limitation. The BW engine will actually render up to 512 sprites per map, if I am not mistaken. You can actually change the limit in the ScmDraft profile settings. 250 just happened to be the limit the original StarEdit allowed.
There used to be a believe, or rather a superstition, that high sprite numbers in a map would cause attack bugs (most notably the Valkyrie bug), but that us actually not true because weapon sprites (and moreso Valkyries specifically) have their own (and unfortunately rather low) sprite limits which, when exceeded, will prevent sprite based attacks.
Well, there is a total sprite limit. I think, which factors in all sprites in a map, including units, map sprites and weapon sprites, so it is possible a game could max out on sprites in an 8 player game, just like hitting unit max can be a problem. But usually hitting the unit limit is much more limiting, so I don't think it would be much of a problem either.
From my experience in trying to make a forest themed map I've found out that there is actually a sprite limit for doodads but its not at 250 but 500. Going over the limit just causes sprites past the 500th one to not be shown in game... modified by Clipse
As I said, you can set the editor limit to arbitrary values in ScmDraft. Using the 500 the engine can actually handle is probably the best choice, though.