People are always in search of images that they can use, and so I have found a few more search engines that can be used for exactly that purpose.
PicJumbo says "totally free photos for your commercial & personal works". There's a search option, or you can approach via categories. Didn't find any for libraries or books I'm afraid, but the pictures there were large, very good quality and in a number of different styles.
Gratisography is another CC site with free high resolution images which can be used for personal or commercial projects. Only a small number, and no search option, but the pictures are really attractive.
Pixabay has a larger collection - there were over 200 'library' photographs and over 700 books. Filters are available to reduce the number, and quite a lot are clipart or icons.
Photopin offers free photographs for bloggers and creatives, and they all seem to be CC with attribution. Nice search function, which pulled up lots of library and books pictures, with opportunities to filter as well.
Unsplash doesn't have a search function, and the images are mainly of places/geography but they really are stunning. 10 new pictures every 10 days.
New Old Stock is a fantastic site. Lots of old photographs in the public domain. Marvel at British Transport trams! Enjoy the 3-man bicycle! Look at firemen gorging on doughnuts! It'll keep you amused by the hour. No search function though.
Thanks to Dustin Stout for his list, which I cherry picked. You can see more options, plus stock sites by visiting the link.