As a Dungeon Master, I strive to create an awe-inspiring image with only my words, so I'd like to hear of things you as a DM or player, have heard or told during a campaign you found really interesting or impressive.

I don't have anything handy at this moment, but I commend the Matt Colville series on Running the Game to you.  Matt does a great job of providing descriptions.

For my part, I like to describe smells when I get to an interesting place.  If I describe a coastal fishing town, I would include a remark about it "smelling like salt water and decaying fish."  If I were to describe the smell of the guardhouse (inside) during the warmer months, I would add, "... and the smell of perspiration hangs heavy in the air."  A typical tavern smells "... and the odor of heavy kitchen foods, spices and spilled ale is more notable than the smell of smoke from the fireplace."  In a cave, "... the air is cool and still with a touch of mildew odor."  The stable, "smells like stale horse dung, apparently not having been cleaned in over a day."  The blacksmith smells "... of the leather apron the smith and his apprentice wear and the fire never goes out, but also the smell has a hint of that peculiar molten metal smell; something very distinct that you recognize right away but you don't know why it smells like that."

So I like to add smells to my list of descriptive elements.

That is actually really good, I never thought to describe smells, it would be an excellent way to bring the campaigns to life.

I described a secret door...as a DOOR!!!!!!!!! A secret door with a bit of corrosion on the backside of it

Music Scout is super correct on smells. Also a big up is choice of adjectives and your words. Also describing rooms in unique ways that we don't normally, as it sparks player creativity naturally; ie, Saying a room is Morose (Very Sad) before describing its interior which will back up that idea. It's a small edition to characterize an area before describing its contents or going deeper, it sets a standard and your players will naturally see how things fit to that standard thus reinforcing it and usually expresses things you want your party to feel in a cleaner way anyhow. Usually people start with the room and layer the adjectives on, but instead the adjectives, the feelings should be the base of everything you are making.

Starting with a room means your players have a blank slot they are adding things to.

Starting with *Described* room means your players have a style they will adhere to that they will edit from there and will have a closer creative image to what you are tying to do.

For a tiny example of how it sets off a better description immediately:

You enter a frigid and unsettling room, in the center lurks a tarnished doll, whose eyes, though cracked, seem to be an endless black void.

Compared to:

You enter a room, it is frigid and unsettling and in the center lurks a tarnished doll, whose eyes, though cracked, seem to be an endless black void.