I work closely with infosec day to day.
There's a simple solution to this which will put the paranoia and fear to bed.
1. Take all photos from a cheap camera used only for that purpose. Never use your good camera for questionable photos, and never use your cell phone camera for those either.
2. Strip all EXIF/metadata information using a tool appropriate to your OS.
3. Resize with a simple utility not known for storing metadata, or Photoshop if you know when and how to disregard this advice.
4. The target size should be reasonable. 1024x768 should be enough for anything which is being shown on a screen. We're not making prints nor is this a photography competition, so keep it reasonable.
5. Run your EXIF/metadatastripper again.
No metadata, camera fingerprints, or latent physical fingerprints will come through.
When you're done for good, smash the camera and throw it into a dumpster.
Once the basic EXIF/metadata is gone, there should be more of a concern with ill-advised objects appearing in the photo, be it a closeup of an actual finger, a national/provincial/state flag on the wall, a specific combination of books, rare glassware from a small manufacturer, other low-volume specialty equipment, etc.
Seemingly innocuous details can be enough in combination. What someone thinks is irrelevant may not be, especially if they're one of only a few individuals in their province or state to be pictured with a certain piece of equipment, with a certain glassware set (pictured in another thread), and ordering a certain unwatched but low-volume chemical, from a certain supply house.
Paranoia should be directed at removing superfluous information from the contents of the photos rather than stressing too hard about scary but unseen data in the image files themselves. A Ford isn't suspicious, a specific model of a Ford isn't suspicious, and a specific color of a specific model of Ford isn't suspicious. However, if a specific make, model, and color, of a older year, with distinctive wheels, and out-of-province plates is seen leaving the scene of a crime in a small town on the other side of the nation from where it was plated, then that becomes a damn good description of the suspect. Apply that thinking to the contents of photos and don't be done in by what you've bought and how you've decorated, especially if there is a concern that unnecessary flair might be used to authenticate photos collected online to a discovered lab premises offline.
