Set up a Pinterest Board for each of your titles. Then post pictures related to your book. The locales especially. When I am reading a book I especially enjoy, I Google (or Bing or Chrome) to get some visual references, history, or facts about the era or real people mentioned. You could accumulate the same on a Pinterest board. Then use the link to the Board everywhere, such as your email sig, on your book website etc. Be sure to include a pin of your book’s cover with a link to Amazon so people can buy it at once.