I wish I was there! I think there is something so beautiful about stark tundra! You've captured its beauty well! I love the composition of the rocks in the foreground.
This does not really meet the challenge for me. It is not really something light against a white background, but is a hard landscape with a white sky. As a photo, there is not enough subject to hold my interest (too much space between the foreground rocks and the mountains.)
The white background that the challenge called for is presumably the sky? You have captured the barren vastness of the tundra well, but there isn't enough here to compell me to carry on viewing. The forground rocks add interest, and the far mountains bring my view back down to the wasteland, but it all seems a bit flat and uninterseting.