The logo looks much better as does the tongue I've had a little play and perhaps taking that layer of brown pixels off where the tongue leaves the head (next to the top black pixel of the crease in the tongue)

Okay, tried changing the sprite accoring to your suggestion(s). How is it now?

I'm still not sure about the mouth/tongue, though. Maybe I should remove the tongue altogether if it's problematic enough...

I like the overall shape and colour, the rear (as in furthest from the viewer) could be a bit darker, more like the underside of the creature and I think the tongue needs work, it looks more like it's holding a bitof meat in its mouth rather than being part of the creature, though I can't advise you on how to fix it. Perhaps make the side of the mouth that is partially open darker?

Edit: I think you should bring the gl logo down a bit to make it look more like a branded rump. :)