The neraphim (Planar Handbook) are specifically from Limbo, but they could fit in elsewhere. Also, anyone with levels in the Chaotician PrC from the same book.
The gibbering mouther would fit in well in a chaotic environment.
There's a chaos-borne template at, IIRC, Green Ronin's website.
You could use the Living Spell template (MM3) on Chaos Hammer or some other similar spell.
Ragamoffyns (MM2, I think?) would also fit in well if it's a plane where travellers are frequently waylaid -- the ambient chaotic energies animating the goods they've left behind.