I've compiled a list of all the Pathfinder Monsters released under the 3.5 rules that have yet to make the jump to PRPG rules.
It would be great to continue seeing these monsters updated in future Bestiaries and I suspect we will. However, not all of them are campaign world generic, so with that in mind how about a smaller, Inner Sea Bestiary for the Chronicles line.
forge spurned
Azlanti chariot beetle
granule construct swarm
nightmare bats
chatterer swarm
son of perdition
dhabba
sand eel
frosty chiseler
bloodless vessel
arcanaton
tongue of rebuke
wings of protection
ghalshoatan
asakku
sandwalker
torthune
crepitus
bonestorm
cinder wolf
havero
red reaver
chained spirit
danse macabre
akaruzug
darklands sentinel
swamp barracuda
blast shadow
cutlass spider
ghonhatine
irnakurse
carrionstorm
buraq
edimmu
unchosen gnoll
emkrah
hadhayosh
rukh
rukh, juvenile
miengu
black jinni
get of Iblis
gandareva
sruvara
zahhak
smoke haunt
skull ripper
argorth
mother of oblivion
scanderig (forgefiend)
ercinee
star monarch
crag spider
kuchrima
harridan
hungerer
dream spider
rajput ambari
sikari macaque swarm
Black Echelon operative
guiltgorger giant
wooden protector
shadowy lurker
croaker
gutdragging lurcher
roseblood sprite
fell flotsam
hoary muntjac
snowdrifter
Hungry Mist E2
Organ Swarm J1
Elemental Swarm S1
The following are Unique Monsters and not likely to be seen in a Bestiary, but might make good additions in and Inner Sea Bestiary.
Prince in Chains
Achaekek, the Mantis God
Lawgiver
yethazmari
night monarch
Ahriman
Xotani
Sunlord Thalachos
Menotherian
Thais
*Note
Achaekek and Ahriman are not likely to be given stats again until rules are made for Epic play. Even then these two being a God and Demigod are not likely to be given stats simply because Paizo frowns on Stating up deities.
The following two monsters were only given stats with special permission. They can not be reprinted again unless Pazio is again given special permission for them to appear in their products.
deep crow
coeurl
Lastly we have templates.
runeslave
Osirion mummy
nosferatu
black blooded
sea-sworn
necropyre
dark ice creature
wyrmskull
painted creation
So I wouldn't mind seeing a Monsters of the Inner Sea Region 64 page book in the Chronicles line to bring these monsters into the fold. :)
Should an Inner Sea Bestiary happen I would recommend the following since they have the strongest ties to Golarion and would not make the best options for a non campaign specific bestiary:
Azlanti chariot beetle
tongue of rebuke
wings of protection
cinder wolf
unchosen gnoll
emkrah
get of Iblis
hungerer
Black Echelon operative
Prince in Chains
Xotani
Sunlord Thalachos
Menotherian
Thais
Lawgiver
yethazmari
night monarch
runeslave
Osirion mummy
black blooded
hmm, only 20 monsters out of a possible roughly 58-60 monsters that could fit in a standard 64 page Chronicles book. Plenty of room to play with. :)
On a side note:
Ghalshoatans would make a great addition to the Rakshasa group of evil outsiders presented on page 224 of Bestiary 3. They'd have to be changed to outsider native but that's not a big deal, the Xacabra lost its Demon status when it made the jump to Bestiary 2.
Crepitus would make a great addition to the Asura group of evil outsiders presented on page 21 of Bestiary 3. Especially since they are already set up as being a divine rejection.
And Arcanaton just screams to become the name of a group of Outsiders since they are already described as essentially being arcane elementals. I could see the Arcanatons having a similar relationship to Nethys as the Pyschopomps have to Pharasma.
Just some thoughts.
Someone with such an intense love of Golarion monsters would be greatly appreciated on the wiki (hint, hint)!
On a related note, check out our Monster Index, a nearly complete listing of all Golarion-specific critters published by Paizo.