I've started to add some backstory, and some set pieces to the game.
Also on YouTube
Since the castle is a tourist destination, it makes sense to have informational signs in each room explaining what the historic role of the room was and supplying some interesting facts. These facts are purely made-up and fake, tee hee.
Moreover, these signs are setting-space for inserting important backstory details later on. For instance, the castle may or may not have been once occupied by a mad wizard. If that's the case, then we can make allusions to it on certain signs, the game design equivalent to literary foreshadowing.
Other signs just serve the purpose of making the setting more consistent, and adding humorous details for the player to chuckle at. If we do a really good job, we can create the effect of causing for the player the "I wonder what *that* sign says".
A set piece is some visual resource that exists in only one place. These seem a bit expensive to make: for instance, the set piece I most recently created was a suit of armour. It took around two mornings to put together.
What a set piece does I think is help to create a bell curve for uniqueness of game visuals. Graphics in a game will usually repeat many times, and the player will notice this (of course).
Now imagine, for each graphical object of type T, it appears N times somewhere in the game. We look at all objects of type T and count their N instances, and create a graph using it.
If every object appeared 50 times, we would have a flat curve. My theory is that this is unnatural. I think in the real world, objects occur according to a bell curve. So for instance, some objects are relatively plentiful (these exist at the center of the curve) and some are quite rare (these exist at the ends of the curve).
If we tailor the repetition of objects to a bell curve, this will more closely match yours and my day-to-day experience with discrete objects in the real world. Laptops are more rare than leaves, but not so rare as an ancient ruin or as Ankor Wat (which is more like a real-world set piece). Houses are fairly common, but again not as common as leaves.
When you get to grains of sand, you could say they are so common that they break the bell curve, but we don't normally perceive them as discrete objects. Instead, we group them into beaches or maybe conceive them as handful-sized-lumps, in which case they probably fit somewhere in the same realm as leaves, rocks, blades of grass, and that sort of thing.