They have just entered a room which contains a huge, evil, dangerous lizard. Naturally they'll first take a detailed inventory of the room's ambience before noticing the rather large gecko which is about to fry them to a crisp. That makes perfect sense. Just adding about and probably in judicious places will at least preserve the illusion that the players aren't doing mapping at a level of detail which is quite implausible. It is not the business of the GM to dictate how the appearance of something makes the player's characters feel.
Authors have control over all characters in a story.
GMs don't have control over all characters in a game. GMing isn't writing. It isn't even theatrical direction. It is a cooperative, mostly ad-libbed venture. Live with it or give up the reins.