Hmm... the closest I can associate Crom with is a deity mentioned only in previosu eds. of AD&D--the northern god Kos, from the Lankhmar/Nehwon mythos. He was described as the god of doom--more or less as a master of mortal fates.
You may want to have Crom be more of an earth-associated, non-Good version of Odin from Deities and Demigods (though with both eyes, of course). Or a mix between Odin & Tempus from FR. However, Crom doesn't really come off as chaotic, per se, but more indifferent. One to enforce rules in some instances, then ignore them in others. Crom seems to be a sort of war & death god, with an underworld theme (since he lives under the mountains).
My rough guess on the deity would be:
Crom, N god of doom, mountains, conflict/war, earthquakes/avalanches
Domains: Death, Destruction, Earth, Strength, War (perhaps Cavern & Metal domains from FRCS--Cavern as an extention of the earth theme, and Metal due to the "Riddle of Steel").
Symbol: Mountain, throne in a mountain, or something along those lines (or perhaps the wheel symbol that Conan wore in the movies).
Favored weapon: Longsword (or battleaxe)
Hope this helps.