Well, we can't be sure if the painter of the picture is well versed in Scriptures or that he has drawn the positions of various Gods exactly as depicted in our Shastaras.

However,one get a good summary of the positions of Gods,Rishis,Vedas etc in a Cow's body  in the "Grihasta Ashrama" chapter found in the [Skanda Purana][1].

> Cows standing for virtues do fall in the care of Brahmanas as the
> former represent Vedas-Rig Ved being the back of Cows, Yajur Ved being
> their middle portion, and Sama Ved their ‘Kukshi’(stomach); ‘Ishta’or
> Yagnas and Yagas and ‘Apurti’ or Wells, Tatakas, Gardens etc are their
> horns; Veda Suktas are the body hairs; Shanti Karma and Pushti Karma
> are their dung and urine; ‘Aksharas’ are their feet; Cows live for
> their Pada-Krama-Jata-and Ghana Paatha viz. the various Mantras;
> Swahakar, Swadhakar, Vashatkar and Hanthakar are the four nipples of
> their breasts, each of the nipples representing Devatas; Pitras;
> Bhutas, Rishis, Munis and Sureswaraganas; and Human beings
> respectively. The last nipple yeilds maximum milk to human beings.Thus
> the responsibility of looking after cows is squarely on human beings

The above words are those of Maharshi Vyasa as told to Yudhishtira.

  [1]: http://www.kamakoti.org/kamakoti/details/skandapurana31.html