Time to quote the book
First picture:
"The 'Song Engine' is an example of ancient Mudokon technology that is meant to harness nature's energy to create spiritual music that, in turn, reinforces and protects the natural spirit world. As the living waters of the river flow through the Song Engine, music plays to welcome friends and ward off enemies. If a threat persists, the giant wooden sentinel can be brought to life with the chimes and drums as its heartbeat. However far the music carries, the sentinel can bring its strength to bear."
Second picture:
"This Mudokon river city, hidden deep within an ancient swamp, is a concept for the way some desperate holdouts may have come to build a piece of Oddworld's bright past." There was no name given; the caption only said "River City."
Third picture:
"These designs depict a monolithic shrine at the river's source called Ma'Spa. In these pools ,the Gabbits would spawn the next generation and continue the cycle of bringing life to the Mongo River." The caption said "'Ma'Spa' by Raymond Swanland." I'm not sure if it was Raymond Swanland that designed it, or if he just created the mentioned picture. On the same page there was another concept painting of Ma'Spa by another production designer, Gautam Babbar. (Personally I prefer Babbar's version
)