While June is LGBT Pride Month, free LGBTQ-themed stock photos are useful year-round. Here’s some sources of free photos and stock images that’re LGBTQ friendly. Most of these are offered under a Creative Commons license.
Pixabay offers a variety of images that’re free to use. Stock clip art, including of pride flags, icons, etc. are also available, which is a nice aspect alongside the photographs. If you need an image of a pride flag (either art-based or photo-based), Pixabay’s a decent source.
On the down side, Pixabay (from my searching) doesn’t have many photos featuring LGBTQ people of color. There’s also Pixabay’s recent change to its licensing, dropping Creative Commons in favor of a proprietary license.
https://www.flickr.com/search/?q=LGBT&l=4 (CC BY license)
https://www.flickr.com/search/?q=LGBT&l=10 (CC0 public domain license)
Flickr features plenty of LGBTQ Creative Commons photos, with some also featuring people of color. Many of the photos seem to be from various Pride festivities around the world. Some also include people of color.
Wikimedia Commons offers some stock LGBTQ themed photos and graphics. However, their quality and exact copyright/Creative Commons license may vary.
Creative Commons.org offers the ability to search for LGBTQ tagged photos from multiple sources.
Hopefully the above is useful. If you happen to know of any other Creative Commons or public domain based sources of photos, please let me know in the comments.