Hmmm...not sure if it's the fact that the bunny's head is mounted that is making it creepy.
In fact, I'd say it is the fact that the animals are "sorta" looking at the viewer or boy...it is kinda ambiguous where they are looking honestly.
It would possibly be less creepy if you just had the animals staring ahead (to the left of the frame).
However, even then, I can't decide if the boy is looking up with tears welling up in his eyes or is like "hey...wait a sec..." which is kinda funny--but still kinda sad.
It could be that the overall color pallet lends itself to a melancholy feel.
Personally, I think the ottoman is good as is. In fact, I think you've mastered form, lighting and material on 90% of this piece. It's just incredibly good.
The one crit I would have is that the animals themselves are coming across a little "fake"--not sure if that's the right word. For example, the deer neck (which comes across as very long, imo--maybe shorten a tad?) appears to be made of a smooth material rather than short fur.
But this is just so great overall. Portfolio piece for sure.