If all players put this much thought into their own custom chapters/craftworld/septs then the 40k games table would be a much happier place.
As a biologically educated chap with a passing interest in animal physiology, I have one comment:
The Ulvs may be alien and whatnot, but they still need at least two eyes for binocular vision. This is vital for any predator who needs to judge distance with any degree of accuracy. Without binocular vision theyd be constantly bumping into things that they thought were big prey far away but were actually small prey up close. Of course, thats liable to be lot more inconvenient for the small squeaky prey animal than the Ulv, but still, its a bit of a design flaw. Now, notice I said at least
two eyes. If you so desired they Ulv could have 4 eyes - two small, glowing day ones and two big black twinkling-in-the-frozen-starlight night ones. Alternate pairs could close seasonally, so that during the summer months the night-eyes could be squeezed shut (too bright), but in the winter the day eyes would be closed. The chapter symbol could still be a red eye, as drawing a four-eyed thing on a shoulder pad would be a bit of a fiddle.The chapter could have some sort of fetish for night vision goggles or implants or similar. "The ultimate predator can see in the dark. And so can we!" kinda thing.
Just an idea, though - its your chapter, so feel free to do as you like with it
ps - I'd recommend you read "Prospero Burns" by Dan Abnett. Its all about pre-heresy space wolves, and so far what Ive read of it is all very viking clansmen, fjords, glaciers, big hairy sea beasties, and axes. Not too dissimilar in feeling to what youre after with the Grim Wolves, I think, although being from Sweden you'd know more about these things than me, I spose.