I spent some time in the Vienna Natural History Museum one day in September 2008. This is the best image of the Venus of Willindorf from that session.
Opinion is divided about the pattern around the head.
Some say it is braided hair, others say it is a woven (or crocheted!) hat pulled low over the face. There is evidence for woven textiles from that time. It could also be basketry. Note the "golf ball" venus (at the bottom of the page on the link) from Kostienki, which is a head totally covered with basketry, and the similar full figure with the head almost covered in a similar texture.
But all agree that it is deliberate, to hide the face. The question is, why?
All sorts of theories have been put forward - that it is an anonymous female, or that it is the earth mother, whose face not only cannot be seen, but must not be seen.
All conjecture, and your guess is as good as anyone else's.
The thick circles at the top of the breasts of the Willendorf venus are vestigial arms. If you look at the figure closely, you can see the matchstick arms starting at the shoulders, and continuing down the body and across the breasts. Look closer still, and you can see bangles or arm ornaments at the wrists. Even hands with fingers are indicated.
Depending on your browser, you may have to click on this image a couple of times to see it at full magnification.
Photo: Don Hitchcock, 2008
Source: Original in the Vienna Natural History Museum