Increase scale of detailed image view

[SilasPeters]

The current detailed image preview is not that much bigger than the preview of a picture.

Suggested change is just increasing the size of the pop-up panel. Even better would be if the image would be displayed almost-full screen, with at the top left a 'back' arrow, and thumbnail previews of neighboring images at the bottom (which is collapsible). Within this view, you can cycle through the images.