Yeah, the first photo is from the Zilker "great lawn".
I think the 2nd photo was taken from a house overlooking the city west of Mopac. The man who took the photo does work for real estate companies selling houses in West Austin. The view isn't from the Mopac Bridge since it's way too high for that to be since you can see the river so far down in the photo. It's not from the Zilker Clubhouse either because the Frost Bank Tower doesn't show up in that view anymore (Spring blocks it).
By the way, this is the link to the original photo. You can view it full-sized here for more detail.
https://www.flickr.com/photos/brianc...33400/sizes/k/