Created in Inkscape using the circle tools for the face and eyes. For they eyes I used a tool that allowed you to set how much of the shape was filled in, the option is available when you first make the object by clicking and dragging the little circle on the outline.
I used the pen tool to create the mouth. I preferred using the pen tool for this part because I felt it gave a bit more character to the face then another generic shape.
The background was created by making a new layer behind the face and layering stars of different sizes and colors to create the design you see.
I had a load of fun making this, I hope you have fun making your own creations!