What does the word 'nimitta' ('sign') refer to in SN 47.8? SN 47.8 (Pali here) is translated as such:


  Bhikkhus, suppose a foolish, incompetent, unskilful cook were to present a king or a royal minister with various kinds of curries:
  sour, bitter, pungent, sweet, sharp, mild, salty, bland.
  
  That foolish, incompetent, unskilful cook does not pick up the sign of his own master’s preference: ‘Today this curry pleased my master,
  or he reached for this one, or he took a lot of this one, or he spoke
  in praise of this one; or the sour curry pleased my master today, or
  he reached for the sour one, or he took a lot of the sour one, or he
  spoke in praise of the sour one; or the bitter curry … or the pungent
  curry … or the sweet curry … or the sharp curry … or the mild curry …
  or the salty curry … or the bland curry pleased my master … or he
  spoke in praise of the bland one.’
  
  That foolish, incompetent, unskilful cook does not gain gifts of clothing, wages, and bonuses. For what reason? Because that foolish,
  incompetent, unskilful cook does not pick up the sign of his own
  master’s preference.
  
  So too, bhikkhus, here some foolish, incompetent, unskilful bhikkhu dwells contemplating the body in the body, ardent, clearly
  comprehending, mindful, having removed covetousness and displeasure in
  regard to the world. While he dwells contemplating the body in the
  body, his mind does not become concentrated, his corruptions are not
  abandoned, he does not pick up that sign. He dwells contemplating
  feelings in feelings … mind in mind … phenomena in phenomena, ardent,
  clearly comprehending, mindful, having removed covetousness and
  displeasure in regard to the world. While he dwells contemplating
  phenomena in phenomena, his mind does not become concentrated, his
  corruptions are not abandoned, he does not pick up that sign.
  
  That foolish, incompetent, unskilful bhikkhu does not gain pleasant dwellings in this very life, nor does he gain mindfulness and
  clear comprehension. For what reason? Because, bhikkhus, that foolish,
  incompetent, unskilful bhikkhu does not pick up the sign of his own
  mind.
  
  
  
  Suppose, bhikkhus, a wise, competent, skilful cook were to present a king or a royal minister with various kinds of curries: sour, bitter,
  pungent, sweet, sharp, mild, salty, bland.
  
  That wise, competent, skilful cook picks up the sign of his own master’s preference: ‘Today this curry pleased my master … or he spoke
  in praise of the bland one.’
  
  That wise, competent, skilful cook gains gifts of clothing, wages, and bonuses. For what reason? Because that wise, competent, skilful
  cook picks up the sign of his own master’s preference.
  
  So too, bhikkhus, here some wise, competent, skilful bhikkhu dwells contemplating the body in the body, ardent, clearly comprehending,
  mindful, having removed covetousness and displeasure in regard to the
  world. While he dwells contemplating the body in the body, his mind
  becomes concentrated, his corruptions are abandoned, he picks up that
  sign. He dwells contemplating feelings in feelings … mind in mind …
  phenomena in phenomena, ardent, clearly comprehending, mindful, having
  removed covetousness and displeasure in regard to the world. While he
  dwells contemplating phenomena in phenomena, his mind becomes
  concentrated, his corruptions are abandoned, he picks up that sign.
  
  That wise, competent, skilful bhikkhu gains pleasant dwellings in this very life, and he gains mindfulness and clear comprehension. For
  what reason? Because, bhikkhus, that wise, competent, skilful bhikkhu
  picks up the sign of his own mind.”


What specific thing does the word 'nimitta' ('sign') refer to above in SN 47.8?
In the same sutta, buddha said:


  tathā hi so, bhikkhave, bālo abyatto akusalo bhikkhu sakassa
  cittassa nimittaṃ na uggaṇhātiฯ.


Then said about satipaṭṭhāna:


  evameva kho, bhikkhave, idhekacco paṇḍito byatto kusalo bhikkhu 
  kāye (=base, object) kāyā-nupassī (=sati-cetasika) viharati ātāpī 
  sampajāno satimā, vineyya loke abhijjhādomanassaṃฯ


So:

cittassa nimittaṃ (base[=object] of consciousness) = satiya paṭṭhānaṃ (base [=object]  of sati).

The other name is kammaṭṭhāna (base[=object] of cetanā).

P.S. Sati must arise with consciousness.

I'm sorry for my first mistake answer.