Increasing / choosing resolution of Generated Previews?

If I switch to Large thumbnails view while browsing a blend file, the Generated Previews are just too low-res.
I know a higher resolution would result into larger .blend, but maybe there could be an option to choose from a variety of resolutions, including a large ones?

The thumbs are also weirdly dark when models use Shadeless materials.

I would be happy if anyone can address these & fix / implement a solution.

Thanks :slight_smile:

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