Well, Goran specifically asks for a square logo with a minimum size of 512 pixels. I’m a bit puzzled by this as most loges are not square.
You must not see the current web page at https://www.emap.no/wordpress, as I’m constantly trying to find a workaround. My current solution is to make a square transparent image with the logo placed in the top of the image. The result is that the dark header line becomes much wider than wanted, and thus wastes precious vertical space. To compensate for this, I hade to make the logo smaller than I wanted.
I have been unable to find a solution modifying the CSS, which could (should?) have been another option.
A better solution is to allow rectangular logoes in the Goran theme, as most logoes indeed are rectangular.