I don't know why but Rhino still doesn't have a feature similar to sketchup's FaceMe. By using only a billboard image instead of a heavy 3d model, FaceMe is one reason why sketchup scenes can be so light weight. Years ago I made a rhinoscript to accomodate this, but recently I adapted it to grasshopper so that it can be more controllable.
Simply stated, this is a grasshopper script that reorients the billboards to face an attractor point. I've also attached some jitter commands to create some variation. Then bake the new billboards and delete the initial surfaces. In the future, some vb/c# work can link the attractor to the camera location.
Note that for now, all billboards textures must be assigned by layer and differently billboard images need to be grouped and baked separately.