These are not final renderings. You get an idea of the concept, but in no way are these final. This is the same process as WSC...early SketchUp model views are leaked, then final renderings are released at time of formal unveiling.
Aerial view was produced using SketchUp, which is not a final rendering tool. Background goofiness (Jardine, the Rec, etc) is just plan view of an old campus base map, most likely from Facilities Planning. The end zone rendering is an existing photo looking north, with an elevation of the NEZ composited in using Photoshop, or similar, along with a clone of an image of the student section, which is why you see the band behind the goalposts.
At the spring game, you'll see more detail that is closer to what is to be built...maybe even 3D fly throughs. These images are lower quality concept renderings, but they've served their purpose- whet the appetite of fans and donors ready to open their check books. On April 26th, the renderings will be real, and they'll be fantastic.