Set image size to be percentage of screen

[Sergej]

I'd like to see an option where I can choose to set the image to be a percentage of the screen, not just full-screen or fit to screen.

[Sergej]

I did not mention the reason for this request:

If I include High-Res images in for example 1000x800 + 800x1000 size, with added border, on many user's computers, an image in portrait layout will fill the screen from top to bottom. It would look nicer if there is a little space between top and bottom to get a 'floating effect'. It makes the image stand out more, especially with random positioning.

thanks,

Sergej