Unfortunately it is not possible to show a transparent background other then
white, There have been more issues about it in this forum and you also might
want to add a feature request for.
Only I don't know if it is possible at all, I remember trying to find out if
other app's that are showing thumbs can do so and I can't recall one that
did show transparence backgrounds, some convert to black some to white.
Is there a way to get Bridge to show the transparency on files? I thought this
would be automatically built-in, but maybe not? When I browse a folder of png
files they all have white backgrounds on them even though the actual files
have transparent backgrounds. Do I have to enable transparent backgrounds
somewhere? I can't find any option to do that.