I was also looking for them and thought the wallpapers would have been related to Bing's Image of the Day, but narrowing these to mountains at https://www.bing.com/gallery/ didn't work, the images aren't there. Sorry.
I ended up picking up one of their images available for download (not all of them are), as they look equally great on the lock screen.
Cannot find theme anywhere except for the one already posted:S
I tracked down the Graphite Gold wallpaper, it seems to be the Convict Lake; there's plenty of images on Flickr but with slightly different light than the Laptop one