One of my favourite things for sharing my images online is to use the photograph of the time I'm there with the scene in the background. You can see this in my sketch of the market (the cover image). I like to use this technique to share my images publicly because it shows where I was standing when I created the sketch and it also shows the object or the scene that I was sketching. But the other reason for doing it is it distort the sketch image making it difficult for people to extract that and reuse without your permission.
Now I know this doesn't stop it completely but it does make it more difficult. Now I guess you could use AI to help do this for you but at least you have to know some skill to do that. In the same way if you put a copyright on your image, there's nothing to stop AI extracting that and removing it.
So the lesson here is I try to make it difficult without making it apparent that I'm making it difficult.