Uncle, your work is really great, but the toilet paper(I don't know the translation of this to english) you put in the face is in some points looking cylindrical cause you're use too much shading in those toilet papers.
As you can see, I used the same lines to do the toilet papers. In the first I put a good amount of shading, but it looks cylindrical, and I don't want it to happen if I want to create something flat.
In the second one I just put the shadding really near from the base lines, cause they're flat, so there will be a great area where the light will get. The space that you use in something to shade it is crucial to determinate the shape of it.
In the majority of the places you do this ^
But you can 'fix' it. This way \/
I hope I have taught you something with this post. (: