Social media is very visual. Platforms like Snapchat and Instagram have a lot of potential, I don’t think the majority of libraries have taken them up yet. Even on “traditional” sites like twitter and facebook, photo posts get much more engagement (in terms of metrics – clicks, likes, shares). They can be a great way of communicating what’s going on in the library. Photos of events, displays, new arrivals, new services, can communicate a lot. There’s always the issue of getting permission from people to use their photo, but it’s as simple as getting them to sign a clearance form.
One thing I’ve seen libraries do is set up an interesting “selfie” opportunity as part of a display or exhibition and asking patrons to take tag their photo with a particular hashtag can build community too. And maybe running competitions where users can send in a photo?