I have very strong opinions on description, so my philosophy is to describe everything.
See, if you want your story to seem as real, as three-dimentional as possible, then the reader has to be able to visualize everything in their head. The only way for them to see the fic is if you provide them with the description. Your reader isn't supposed to be guessing what everything looks like-you should be giving them strict guidlines, telling them what they should be seeing.
I like to think of a story, a scene as a picture you are trying to paint for your readers. YOU have to provide them with the materials-the canvas and paper as the main base, being the backbone of the story, the shape of whatever is to be drawn on the paper is the plot, and the paints, the colors, is the description and character work. Without the right blend of colors and good shading you won't have the desired effect on your readers.
So I suppose you can guess what my view on this is. XD
But all metaphors aside, I think that your characters' surroundings are very important. If you want your readers to feel like they're actually in the story, standing right next to the character, then they need to know just where the character is and what its like there.
Describing surroundings also helps create a mood, which is always something you want to set so that your reader can get a good feel of the story.
Plus, if it's in a home setting, then the appearance of the building also hints as to the personality of one of more characters. It can also hint the social class of the family-how rich or poor they are. So the quality of a character's living place also gives insight as to what kind of person they are, how they live their life and even the way the think, as well as their finacial status to boot.
A LOT of people make the mistake of totally leaving out description for buildings, which is really bad. Just about every trainer fic starts off with a kid getting out of bed, getting dressed, running downstairs, sometimes eating breakfast and then running out the door to the nearest Pokémon Lab, and just about every one I see doesn't say a word of what the house is like, often saying (after I ask them) that it's just a 'normal house'. The truth is, everyone thinks of a 'normal house' differently. No two houses are the same, because everyone takes care of their home differently.
I know all I really said was about houses, but it can apply for other things as well, if you think about it.
With a Pokémon Center, I think you should always provide description, to give it an atmosphere and make it a place for trainers to rest and relax after a long day's training. In Negrek's example, it was a shelter from the elements, a place to rest after walking all day in the rain (which can represent misrey.
You'd be surprised with what can happen in a PokéCenter-all kinds of people can be there, if you describe them, there could be events announced there and all kinds of things. If a trainer is feeling distracted and caught up in their thoughts, they could see something in their surroundings that the writer can use to relate to the current mood of the character.
So you see, describing the settings is a way to provide all kinds of insight into the world of your character. You can twist this in so many ways so easily to fit any of your needs. Granted, you don't have to describe a bookshelf in a classroom in great detail, but with enough creativity you can take all kinds of paints to create the perfect picture.
~Psychic