I click, nothing happens, or a message meaning no image downloaded.
I can see that I am not the only one disappointed.
There are certainly incompatibilities with some other add-on. I use video-download helper and addblock. I can't imagine desactivating the last one everytime I want to use TabImage saver.
Besides, it would have been more elegant to have a tool to browse the download folder on the parameter page. And even better, to have an option to decide on the fly where to download.