The front cover says "Why you should read C. M. Kosemen's All Tomorrows", and has a small sketch underneath of a large plantlike creature with green tendrils and a large leaf, and a small humanoid creature with a beak (the Temptors from the book).
The next two pages have the text "Because it's fascinating to think about how different life could be," and a simple line drawing showing a worm-like creature with small mole-like limbs tunneling up through the ground, and a snake-like creature with a single hand at the end of their tail, sitting on the surface of the ground (the Worms and Snake People from the book)
The next two pages have the text "because it has some really cool creature designs", and drawings of two strange creatures; one which is flat and quadrupedal, with three hand-like appendages and one long skinny arm, the other is larger and more upright, with eight finger-like legs, a strange diamond-shaped head with a vertical mouth, and one long skinny arm like the other creature. They're holding hands with their long limbs. (These are the Lopsiders and Asymmetrical People from the book and they are very hard to describe. I tried lol.)
The next two pages have the text "because the Colonials and Modular People will make you cry (maybe)". The first page shows the ground covered with flat, square creatures almost like paving stones, with eyes and small tentacle-like appendages (the Colonials), stretching away into the distance. The second page shows two creatures made up of many colourful blobs and tendrils, with multiple eyes (the Modular People).
The back cover has the text "because no matter how bad everything is (AND IT IS), it might be okay in 40 million years?", with a drawing of another worm-creature at the top and a strange-looking green creature with a single long tentacle (the Author from the book).