This is how I do the flickr picture images (there might be another way but this is what I'm used to and not had issues and hopefully I have the steps correct):
First I go to the picture I want and hover over the picture and the pointer becomes a + marker.
Now left click the positive on top of the picture and the picture will enlarge.
I then right click and then left click and select "Page Info" and click on that.
I then get a pop up screen that I have to scroll down to og:image
I then left click on that, then right click and go down to copy and left click and then close out that window.
I then come to this site on the reply and paste it but then have to go to the front of it and add [img] and at the end add [/img]
I can then preview my reply and the picture should show.
This is what I got when I copied the enlarged picture:
and then I added the [img] and [/img] to the above to have this happen: