Extras can add depth to a room. A curious player may well want to know what the painting on the far wall is of. I believe that all nouns within the room description should have an extra description for them. Some extra descriptions warrant extra descriptions as well. For an example of this, read the desk extra below, and then read the nameplate extra.

Michelle Thompson

Room name: Office of the Curator
Description:
Finely, pebbled, light-gray walls surround a small, windowless, square office. Although a profusion of papers rests on the desk, they are meticulously sorted and stacked. Metallic shelves lining the wall by the door are stacked with odds and ends that may one day be displayed in the museum proper. A soft, whirring noise comes from a white device by the shelves.
N
door
The polished mahogany door is framed on either side by shelves containing finds from every known world.

Extra desc:
device white
Air is processed within this purifier to ensure that the precious artifacts are not damaged.
Extra desc:
desk wooden
The perfect wooden desk looks like it belongs in a display. The moldings around the edges have been carved lovingly by hand. A single scratch does not mar the smooth, shiny surface. A small nameplate rests on the desk.
Extra desc:
shelves metallic
The shelves have the silvery sheen of metal. Yet, if you reach out and touch them, they do not have the cool feel of metal.
Extra desc:
odds ends
A virtual treasure trove sits here on the shelves. One person could not in their lifetime collect all these unique items from different worlds. An adventurous story must lie behind each one.
Extra desc: door mahogany polished
Though the stain of the wood is rich and dark, the grain of the wood is still evident in a long, swirling pattern.
Extra desc: papers
Journal entries from adventurers past are stacked neatly and categorized.
Extra desc:
walls gray pebbled
The gray walls have a grainy texture not much larger than sand. Each wall seems to have come from one solid block of rock.
Extra desc: nameplate plate name
Illyana Mynan, Curator