Board Thread:Support Requests - Designing Your Wikia/@comment-24824290-20140509144905/@comment-24661007-20140509190430

^ What he said. I use GIMP 2

I scale the photo so one of the sides matches and one is larger.

Then I use the select tool and select an area that's 670 by 360. Then I use 'crop to selection'  under 'Image'.

That way nothing gets squished or stretched.