The real problem with the footprints is the fact that would kill a person ram and cpu
And I can conclude that you completely have no idea about how games works.
[some boring nerdy math]
For 10 000 footprints you need 10k quads, 1 texture (with different footprints stored in it), 10k position/rotation/scale properties (which are pretty much optional thing sinse footprints can't be moved, only re-placed at new position) and that's it.
Well, it'll be:
4 verts per quad = 40k verts in buffer
6 indeces per quad = 60k indecies in buffer
That means:
40k * 3 (for X, Y, Z coordinate) * 4 (bytes per coordinate) = 480 KB ram for verts (Haha, right?)
60k * 4 (bytes per index note) = 240 KB ram for indeces (Haha, part 2)
In addition, some UV info:
40k * 2 (u, v) * 4 = 360 KB for texture coordinates.
According to my exp., CPU could handle 2M (2 million) verts for a second, that means it could handle 40k verts at 50 FPS. Buuut you don't need to do it by CPU! GPU could handle verts movement as well, and to be completely honest - you aren't changing ALL 10k footprints all in one frame. You shift 10 of them at max.
Keep going. Footprints placement. Is it any "bottle neck"? No.
Since we know any char's position, rotation (aka Transform) and animation frame, we could just make table at very first game launch (we could even ship game with this information!) - which animation frames place footprints and where (relative to creature's position) - read data from table (which, once again, is TINY!) is really fast operation.
[/some boring nerdy math]
In other words:
There isn't THAT much problems with ram and CPU (unless you're going to have 10 million footprints);
10 000 footprints will eat around 1 MB of your RAM (How much does you have? 2 Gb?)
Mostly it's a problem of time - you just cant make EVERYTHING right, you'll have to cut some corners.
And speaking of snow... I bet that's some kind of shader, based on AO, just like one Crytek used in Crysis to create "snow jungles". Yep, it was done with just 1 shader. Brilliant? Sure. Any other applications? Not really... (I mean, it isn't kind of system, which adds real "snow layer" on every object so you can scribe your name on every single surface)