IIRC, Clint also mentioned breeding a pair of snows together and getting blizzards out of the clutch. (Correct me if I'm wrong here, I don't want to put words in your mouth.) I think he also said that the blizzards weren't quite as blizzard-y as would be expected with "standard" blizzards (more noticeable patterning, I think?)
I think what can be guessed is that, at least in the presence of amelanism, Charcoal suppresses the expression of Anery, or partially supresses it. In the second case, this would mean that CharcoalAnerys would look like something "between" a charcoal and an Anery. And it seems like enough of the "standard" ones of either morph already do, so much so that it would be impossible to distinguish the double-mutant from either single morph. (?)
Other tests for this could include pewters het anery, AneryBloods het pewter, and Charcoal Ghosts het anery and ghosts het charcoal, as these would probably be more distinguishable from each other.
I'm not quite sure what could be gained from Anery/Charcoal combinations, though. I think the one safe assumption is that they won't be anything "new" or we'd have seen that by now.
What I find more interesting is which combinations of "anery-like" traits (Anery, Charcoal, Lav, Caramel) might actually look like neither of the single morphs.
This is where something "new" could be created. But there are only 6 double-combinations to be made, and 4 of them look like they have already proven uninteresting:
Anery + Charcoal (shrug, but they're not "new")
Anery + Caramel (Look like Anerys)
Anery + Lavender (looks like one or the other, don't remember which way)
Caramel + Lavender (probable that they have been produced, but nothing "new" has shown up.)
The two remaining "unexplored" combos (as far as I know) are:
Charcoal + Lav
Charcoal + Caramel
Of course this is only what I've been able to gather, and is based on hearsay, so it's not admissable in court, and you should take it with a grain of salt.