"which I did not command" includes (in one interdict) "combining" (any of the above with the L-rd as co-deities).
R. Yossi Haglili says: Because it is written (Ibid. 4:19) ("the sun and the moon, etc.) which the L-rd your G-d bequeathed to all the peoples," I might think that He bequeathed them to the nations (to serve them), it is, therefore written (Ibid. 29:25) "gods which they did not know and which He did not bequeath to them (to serve them)."
R. Yossi says: Elazar, my son, says three things: (Jeremiah 19:5) "which I did not command" — in the Torah; "and which I did not speak" — to the prophets; "and which never entered My heart" — that a man should sacrifice his son on the altar.