Definitely the Two Trees, which puts this image back in the First Age (or before it, if you reckon the First Age as starting with the Years of the Sun). I think the city is Tirion, looking west through the Calacirya, though. Either way, it's a gorgeous image and a great tease for what is to come!
If they get multiple seasons then they could space them hundreds, or even thousands of years apart and only retain the actors that they really wanted/had to. Lots of points in The Silmarillion that they could use for jumping off points. If I was to guess, two stand out somewhat to me; The Forging of the Rings of Power, and The Fall of Numenor. Both have political intrigue and action, to a greater or lesser degree.
To be fair, half of that was spent on securing a license.
Sauron disguised himself more than once, though. It could also be centered around the forging of the rings of power.
Not Valimar. Tirion. This picture (probably) shows the Calacirya, with the Pelori mountains flanking the hill of Túna and the city of Tirion. The Two Trees seem to be in the background.
