Lamassu and Lillend
I don't see much point in putting much effort into celestials - if the players aren't going to fight it it doesn't need a stat block. The Pathfinder Bestiary has acres of pages of celestials which I have never used and am never likely to.
Celadrins, a planetouched PC race, eladrin/high elf with a eladrin (chaotic good outsider) ancestor. Were canon in an article from Dragon Magazine.
Which issue, if you recall? Also, sounds a lot like a 4e/5e style Eladrin with the Celestial type instead of Humanoid or Fey... maybe take the DMG Eladrin and make it Celestial? Wonder if this article was the inspiration for making Eladrin a type of Elf in 4e?
Not really expecting much in the way of Planescape Celestials returning, but it would be nice if they brought back the Asuras and the Lillend. Asuras to give us a CG Celestial that not shaped like a horse, and Lillends because they are keepers of the Infinite Staircase and can be used in a variety of non-related ways as well. Oh, and not Celestials, but - Dabus, please!

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.