A lot of Ral Partha stuff works very well. For example, the wolves that Ral Partha's goblins are on are perfect for wargs in 1/72:
Ral Partha Legacy sells them individually, though they seem ludicrously expensive. They're
very cheap from Ral Partha Europe, but they must turn up second hand all the time, given that they've been in production for 40 years or so.
In general, outsized 15mm animals will work fine (so 15mm wargs as normal wolves), and smaller 25/28mm animals will work well as large, supernatural beings. A friend of mine has Copplestone Casting 15mm
wolves and cave bears in his 1/72 army, and they look great. The cave bears are sufficiently big that he has them mounted individually on 60mm frontages as 'blades' elements in his HotT army of beasts. I'd say the wolves are bang on for real wolves (rather than wargs or whatever) in 1/72.
There are a couple of bears and lions in the
Italieri gladiator set, though the bears are much weedier than the Copplestone ones.