Suggestion: Thumbnail Highlighting
I would not normally use Thumbnails, actually I almost exclusively use Details, but it came up in a thread here so I took a look.
Thinking that the highlighting of the focused file could be improved - more obvious.
In particular, it can be (somewhat) difficult to find the focused file when paging through a directory.
This is what Google does, Google: Servant Salamander.
(Now they are using JavaScript & mouse movements, but the idea is the same).
Changing Colors does help a bit, but it could still be better.