It seems the images that are successful are all PNG files. I can
This issue also seems to be related to the Clipboard API. My thinking behind this is that I cannot use this example page for jpeg/jpg images, but it works fine for PNG.
Are you talking about enkers's comment? I saw their response, which was clearly meant for me and responded. Then they deleted that comment and moved it to where they intended to put it, so I did the same.
I couldn't get past the 4th example of "non-violence" without laughing at how wildly revisionist they are. While each of these had non-violent components, none of them would have succeeded without violence.
I believe the violent aspects of these resistances are considered and included in the overall analysis in the book I linked.
I think you may be jumping to conclusions when you see something that doesn't immediately fall into your own views. Those examples are clearly a simplified and truncated set to quickly get the point across for the purpose of an "About Us" page while there is lots of in-depth information available throughout the site.
If you have qualms with their findings or data, you'd be better off taking it up with them instead of me. I don't purport to be an expert on this subject. I am only relaying that there is plenty of credible research, data, and analysis that shows that non-violent resistance is effective.
Edit
Here you can see how and why the book defines these. The book and its author is a major resource for the website.
Original for more pixels
Art by Cal Kearns