After reading this post, I thought I'd just check the internet for a few of my pictures. I did a reverse image search on my 12 disciples picture (as that's by far the most popular page on this blog) - and I discovered it was on some image libraries.
I'm fine with people downloading the picture for personal use - but I want them to do it from my blog, not a random image library. And certainly not a dodgy image library which brings up loads of popup ads and which my virus scanner warns me has threats on it!
I've probably overdone it now (I can't see why anyone would want to steal some of the pictures!). But you can't be too careful.