My student, Annie, and I have 'finished' our paintings of the Big Rock. Except for fifteen minutes when I started the painting and a few hints and tips after at Art Club, Annie pretty much painted on her own and so did I.
Although we worked from the same reference photo, our print-outs were slightly different colors. Thus our paintings are different too.
Notice that Annie's rock is truer to the actual shape of the original while mine is elongated. I did mine quickly then adjusted it the following week and I was not concerned with duplicating the photo.
Unless you are doing portraits or commissioned work where accuracy is important, it is acceptable to change your work - it is called 'artistic license'.
Without consultation, both of us left out the tree branches on the left. I don't know about Annie but I felt they were just a distraction. It was hard to tell from the photo the color of the grasses in the foreground and we both opted for a green tone.
So! Are we finished? I think I am, but Annie mentioned that she might do a bit of 'tweeking' when we get together next. We will see what happens when I see her painting in person but I think she might be finished too.