I'm not gonna quote 20 posts, but knowing that I was (I think) the first one who came up with the Eastern Unova being frozen idea, I have to slightly apologize. In my excitement I didn't even remember how the 'ice' looked in the picture we got. So my bad. 
But I'm still certain of my theory. I'm only agreeing with the people who say that it doesn't look real enough, not three-dimensionally drawn (...) enough, the ice doesn't seem to fit with how the rest of the region is drawn. So yes, I would agree with the statement that THIS 'ice' is just a cover-up. I still think that Eastern Unova is covered in ice though. Just like Cobraroll said, the fake ice could be hiding major changes to east. Isn't billions of liters of frozen water a major change in appearance? 
AND the smaller picture of Unova in the middle-right end of the picture actually seems to depict real ice (for what my eyes tell me) covering the (Eastern half of the) region.
Trust me, the ICE is definitely there!