Bing Images has added a new “License” drop-down menu item, allowing a modified search for public domain and Creative Commons images. UK users won’t see it, unless you tell Bing you’re located in the USA, via the settings. I’m in the UK, and Bing accepted my country change without query, and without having to “sign in”.
A test search for “Lovecraft” then showed that the straight Public Domain filter is useful with the right keywords, but that the other CC search modifiers give deeply misleading results. Even the Public Domain filter can be misleading. For instance, a simple search for “monster” brought up the logo for the KISS rock band, screenshots of Monster High and Sesame Street, and Japanese anime.