Answer:
A star picture is a picture of a star, but if you are referring to what a pentacle is, it's an old symbol that is classified as sacred. Pythagorean's used this symbol to identify themselves and regarded it as a sacred geometric shape. It's been used by multiple cultures and religions to symbolize different things from the wounds of Christ to the Goddess Venus. It can also represent Spirit's ascension above matter or it's descention into matter (if inverted).
Some other stars that are common is the 6 pointed star, known as the Star of David.
The 7 pointed star, known as the Elven Star.