We have two screenshots so far. Here is one of Pikachu versing something. It looks like it could be a Delibird, but you never know.
Here's a pic of Typhlosion versing a Meganium. As you know, Typhlosion is a fire-type and Meganium is a grass-type. We believe in Pokemon Stadium 3, You get to choose a Stadium. Example: Grass Stadium, Fire Stadium etc.