@wysocki: This request is being tracked here:
Issue 912 – Thumbnail view in file panel
You can vote for it.

Though, if you like Directory Opus, use it :)

Since it's been 15 years, I wonder if this is now a possibility in WinSCP? Directory Opus does a nice job of displaying images over FTP.

Sorry, I do not plan such functionality. It is too much out of scope.

WinSCP is a great software and very well performing. If I could ask something more from it I would like to have an image (or ideally for different file types as PDF etc.) file preview that would be helpful when you need to decide what file you want to access from remote.
Is that something planned for future versions?