Thanks a lot, I have tried this.
But there are still problems:
I have some already existing links, where since months, the "coming soon"-image is shown and "Use Thumbshots.org for dynamic link images" is enabled in the plugin's settings:
If I let this enabled and add in the link editor my own image, then the image is only shown in the link editor, but not at the website. At the frontend/website is still the "coming soon" image from "thumbshots.org".
It seems, that at existing links always the use of the thumbshots.org-thumbnails have priority, no matter, if an own image has been uploaded.
However, if I have enabled "Use Thumbshots.org for dynamic link images" in the plugin's settings and add a complete new link with an own image, then my new image is shown and correctly in thumbnail size.
But if I now disable "Use Thumbshots.org for dynamic link images" in the plugin's settings and upload my own image (800x600 px for example), the image is shown in backend and at the website, but it is not resized to a thumbnail size.
Do you have any idea, how to add an own image, no matter what size, and that this is then resized to a certain thumbnail size?
And how to add afterwards to existing links an own image, where the "coming soon"-image is still there?