Additionally:
Rats: Will always face the column that the Rat King is located in. Any rats within this column will sit upright and not face any direction
Gargoyles: Will always appear in pairs facing one another. Their eyes are indicators of where their partner gargoyle is located (i.e if one has two eyes, the partner is below. If it has one in a direction, it's left or right, and if it has no visible eyes, its above.)
Gazer: Will obscure a diamond of spaces 2 above and 2 aside itself. Only two will spawn.
Big Slime's & Warlock: The Warlock will always appear against the edge. The 5 open spaces surrounding him will be filled with bug slime's (since he cannot have 8, as he will be present in an edge. I do not believe he can appear in a corner).
Lich: Always appears in one of the corners of the map.
Additionally:
-Five chests (And one Mimic) will always spawn. One of the will always contain a scrying orb. That leaves you with two chests that contain health, and 7 revealed health scrolls.
-Though there seems to be no limit as to where the gnome can spawn, because of how the game generates, he tends to remain closer to the edge of the map.