What version are you running?
3.0.18
What's the URL of the page this enhancement relates to, if any?
Show attached images

https://rb.company.de/r/54211/file/2935/
Describe the enhancement and the motivation for it.
If we upload white icons as review request attachments to make a review to an image it is not possible to review that image because the background is also white.
What operating system are you using? What browser?
Firefox, Linux
Please provide any additional information below.
It would be helpful if the background could be the "transparency chessboard" instead of "white". Or a button that allows to switch to "black" background.