I cannot find any option to change the default white background of the layers panel thumbnails in Illustrator CS6, thus all white objects are invisible and I cannot quickly work on them.
I’ve found related questions via Google, but from 2009 and without solution, so probably, someone at present time knows how to deal with this issue?
It’s been reported to Adobe for years.
It has been requested to at least add a light/dark toggle or something.
But, in the end…..
There’s nothing the end user can do to alter the thumbnail background color.