[.:Night Fury:.]

Really the only things that I think need work on is the chin, neck, and belly. Otherwise, it's really good! c:

Some advice:
-Big cats (actually cats in general) don't look skinny. Felines have "fat pouches" that, unless they're starving, make them look a bit fat.
-On a big cat, like this, the legs would look sturdy and not long.
-The tail would be rounded.
-Consider how the muscles would shape the animal: a lowered neck would hunch shoulders, the hind leg farthest back would be on the very tips of the toes when on the ground, etc.
-Feline muzzles are not long like a canines.
-Don't always trust custom-made images! A lot of times, the anatomy is incorrect. Instead, use images of actual animals that closely resemble your creature.

Hope this helps!!!