Posted up on the Paizo.com blog for March 13th are some details and the artwork for the Axiomites and Astradaemons. The axiomites are in many ways the LN analogs for the modrons within Golarion's cosmology (modrons being non-OGL), while the Astradaemons are soul collecting servitors of Golarion's archdaemons (who are largely based on the astraloth from my own campaign / Storyhour).
I'd be curious if folks have any ideas or comments on them. 
These Astraloths certainly give Shadow fiends some competition in the whole soul-collecting game. Of course now I'm curious on who are some of the Archdaemons are, and what their end goals are.
I'm seriously, seriously happy with how the picture of the astradaemon came out. I've also had far too much fun with them (or at least a CR 20+ precursor to them) in my home game.
The picture of the axiomite is very nice, but doesn't play up their nature as (effectively) beings of physically manifest mathematics or nanite clouds assuming humanoid forms as much as possible. We'll be seeing them again, so maybe we'll see some more artwork.
Five monsters total in the book, so three more whose artwork (and identity) hasn't been mentioned yet.
They're described in brief in the PF campaign setting book. But in brief:
Apollyon - The Archdaemon of Plague
Charon - The Archdaemon of Death
Szuriel - The Archdaemon of War
Trelmarixian - The Archdaemon of Wasting
And then there's also the Oinodaemon, who as far as the multiverse is concerned, may or may not actually exist. Except there's a region of Abaddon bound by the domains of the four Archdaemons that doesn't show up on any map, and seems impossible to enter since the terrain warps of its own accord to reroute any nearing its borders. He/She/It may exist as a hidden ruler of daemon-kind. Or he might be dead. Or they might have tried, repeatedly, and failed, and he might be imprisoned, bound and perpetually regenerating, ritually consumed by its children like a perverse sacrament. More on that in the cosmology book. 
And demodands. Let's not forget them. Oh no. 
Pretty! The axiomites seem interesting, though they're not as interestingly alien-looking as modrons. Astraloths/daemons are scary.