I've searched everywhere and I can't find an answer (or even anyone who's asked this before... which is strange):

Does anyone know if there is a way to change the white background on thumbnails in windows explorer? I'm not talking about the background color of the folder itself, but that of the individual thumbnails (for any thumbnail that isn't perfectly square, the remaining space is filled in with white). Preferably, I'd like to make this transparent if possible, or at the very least change it to black.

So, does anyone know if this can be tweaked in the registry or using reshacker? It's really quite annoying.