Glad to see that Twitter confirmed my own experience as not being a fluke. Add an appropriate photo to your tweets and you'll see a thirty-five percent increase in response. I've noticed improvement on any social media site I've posted on by adding pictures. The difference is huge and nothing else adds that kind of increase, not even video clips.
I consider our camera to be one of my most important writing tools. The fact that there is a camera on my tablet is a bonus although I prefer the quality of our dedicated camera. I can't always take the picture I want though so I use some of the free use image sites online. My favorite would have to be Pixabay. There are others that I've used but Pixabay is the one I keep going back to. Simplicity of use would have to be the main reason.
If you read my writing regularly, you will notice that each post or article is usually accompanied by a photo or picture of some kind. When I advertise that article or post on social media I make a point of displaying the photo along with the link to my work. This increase in views has always been quite dramatic. Even if the picture is my own ugly mug.
Originally, on my articles on Pico's Cycling, I credited all photos along with the author at the beginning of the piece. It's important to credit any work that is not your own by the way. I am changing the way I do that. I find it better to put the credit with the picture in the caption. When an article has photos from several different sources that is less confusing.
Best advice I could give another online writer is never forget the pictures.