Really, you even must not copy what you are seeing (exept it is just an exercise for studying certain forms, perspectives and so on). What you finally create on your paper or whatever medium is what your mind is seeing or feeling in this particular scene. It is like eating the scene with your eyes, then it gets "digested" in your mind before you finally create your artwork. I think this is the most important part of the creativity.
Added to that the artist can rearrange scenes to better compose them or he can overdo certain properties of the object or person to better show its character.
This is where the fun starts
Have fun with your paintings!