Don't think theyre personally Donatella's drawings...
A lot of creative directors have illustrators in their team that work for them, or often the designer will dictate a design to an assistant to draw. Stefano Pilati works this way for example.
Galliano is apparently a good illustrator but the ones on this thread are not his personally. You can see his own design drawings in the book 'Galliano' by Colin Mcdowell.
I found some of Alaia's drawings in a book ('ALAIA' : Michel Tournier) and they are really good, a lot of character, although theyre more like illustrations/cartoons as he dosnt draw to design.