Upon comparing the actual Regigigas Ken Sugimori picture to a high quality close up of the pokemon, the "eye" and "nose" Turn out to be the black lines he has throughout his entire body, the yellow head peice is the yellow wristband around his hand, and the "antlers" are his first two fingers (his thumb is hidden behind the wristband). The "leg" is just the ending part of Regigigas' shoulderband and a part of his waist. The brown "fur" may just be bad quality because it's so far away in the backround.
I'm fairly certain about this, but it may just be coincidence and it just may be a Stantler Pre-evolution.