Kinda late on this one :(
The Alien Diaries (German transcription with an English translation) describes Giger's work in the studios and includes drawings, Polaroids showing the monster coming to life, and several still shots from the plentiful film material that Giger took in Shepperton.
More info can be found here
You can also buy the book on Amazon
I really would like to have this book, but for 130 dollars I think I'll pass :( I also really like the cover design depicting the Alien.
UPDATE: Apparently there is 1000 of them.