These are a bit weird. The header doesn't seem too complex (although I still don't quite understand it), it's just the pixel data that I'm really confused about. At first glance it looks like RGBA or BGRA but that doesn't produce any useful results.
Runner 2 (which looks like it uses a different engine, it's not in the BIT.TRIP series but is more of a spinoff) also has .aetex files, but these simply contain uncompressed DDS files after a small header. Maybe that might give a clue to these files, I'm not sure.