All the heads are basically the same. They are worked in the round. The head hangs outside the book and helps the reader find their place easily.
Here are some tips that I have found for adding sculpture to crochet heads. Most sculpture crochet patterns create the sculpture with the stitches as these patterns do, but to add a little more depth and height to the sculpture there are a few things that can be done.
I am not an expert on embroidery but I know some of the basic stitches. I use simple straight stitches for the eyes as this give me the look I want, although I am sure a French knot would work for more rounded or dot eyes such as the Raggedy Ann and Andy Patterns.
For the more sculptured faces of the other bookmarks, I knot the thread and start at the back of the head where much will be covered with the placement of hair on the doll or in this case bookmark. Sending the needle through a hole between the stitches in the back of the head (opposite the eyes in the front), I pull the knot through the head to just past the stitches in the back. I do not pull it all the way through the stuffing to the front but leave it just underneath the back of the head.
I do a few straight stitches on the front over the eye holes. I try to come out at the same spot on the part of the eye closest to the nose and fan the stitch out a little bit on the outside of the eye. When I have the eye the shape I want, I add some additional depth by sending the needle all the way through the head and coming out the back. I go back through the head to the other eye hole on the face making a stitch on the back outside by going over a crochet stitch. (This stitch will be covered with hair.) I pull this stitch really tightly which pulls the front of the face at the eyes toward the back. Then I make another eye using the same method as the first eye.
Since the nose should be higher than the rest of the face, the nose needs to be built up. Using the skin color, I again make a hidden knot by going in through the back and pulling the knot through to just below the surface. Bringing the needle out the front to a point exactly in between the two eyes, I do a series of straight stitches from between the eyes down to a row above the mouth. Again, I bring the needle to the same point between the eyes and fan out the stitches at the bottom of the nose. I continue to build on top of these with straight stitches until I have a large enough nose for the face.
The lips are again simple straight stitches. I found that trying to do a smile just makes the piece look silly so I do a single straight stitch on the row below the nose and two smaller straight stitches just above this.
I hope this helps explain some of the techniques I have found in making simple faces on small crochet pieces such as the bookmarks.