Well, I can't see anything wrong with this photo!
Lovely light, I assume it is evening night through a window? Or did you place a large black cardboard behind your dog and this is actually outdoors?
Whichever way you achieved this light: it is good and works fine!
The all black background enhances focus on the dog and only the dog, and this again enhances all the detail in his fur, which is there and not blown anywhere.
His eye is very much in the centre of the frame, so if you are looking for some nitpicking, here you are: maybe that is a compositional flaw, but actually ...