Generate non-square thumbnail

[Ruke805]

First, thank you for this tool, it's very useful and saves a lot of time.
I would like to suggest in the links tab, in the BBCode option, the thumbnails preset make the images squares and not the real dimension:

It would be nice if you had the possibility to keep them with the original dimensions and not square.

I've checked in the settings and has an option to make a non-square thumb, but I noticed it add a green margin in the image and I don't know how to remove it: