These are the concepts for the light pylons I created for this level. I don't think they were used anywhere else in the game. Also, there are keycard concepts here, too.
This is a closer look at the original idea of the slipgate destination pad. Instead, I started you inside a base section. That pad is really where the elevator lands at the start of E1M1. The drawing at the bottom is the view you should have of the entrance to the base.