I'm glad you like it, thanks for the message. "automatically assign an extension of your or the user's choice to any picture" this is possible, but it would be incorrect and bad behavior. Blindly defaulting to adding .jpg for example to any unknown image, means e.g. a png image could get the jpg extension. Nowadays this should cause no issues, but I consider it an anti-feature because it's simply wrong, so I will not implement it, sorry. Browsers have tricks to determine an extension and will do so whenever possible. If one cannot be determined by the browser, addons are not in a better position to try it. As for the AMO link, I'm surprised firefox doesn't provide that link by itself... So I guess, I might add AMO links to the descriptions next time I work on the text.