Ok, I set 'Wallpaper Download Resolution' to Original Resolution but it still optimizes the image for me PC screen. Why isn't is possible to download in the resolution I WANT?!

That's a stupid idea! What if I want to download a wallpaper for a different device? grrr!

once you click the download button,
it goes through it's detecting routine,
just ignore it once it is done.
then click the "options" button [ upper right area ]
then under 'other options' is a link to "download original"
and that will get you the wallpaper as uploaded.
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hope this helps

toodles,
harmless