Commonly the "side" building you're looking for might be called an "outbuilding". You could also include search words like "detached garage", "barn", "workshop", etc. Most extra structures on a property are in use and become the catchall area for all sorts of things, so they don't lend themselves to attractive photos.
Keep searching, particularly using the suggested terms. With so much expectation on the part of home buyers to see all that they can on the web, we Realtors are making an effort to fill the photo options with as much information as possible.