In response to Hadit93, I have never regarded Astoroth (most often spelt Ashtaroth) as the 'demon name' created by Christians for Astarte.
Ashtaroth in Hebrew is the plural form of Astarte's name, as for the Hebrews it became a general term to describe pagan goddesses. However, I am not suggesting that you are wrong- I think it is more likely that Christians may have changed it after it had became pluralised. I also suggest that maybe the male image you seen was actually a depiction of Ishtar, which kind of is Astarte, but in a different form. Ishtar is her Akkadian counterpart. Although Ishtar is female, she was often depicted as male as that is the gramatically masculine version of her name.
Brysing was quite right, Astarte was (or still is) the goddess of war, fertility and sexual love for the Mesopotamian/Semitic area of the world.
Some confusion came about her and her sister Anath, as they are both so similar that they may have originally been percieved as a single deity. The two sisters together formed the basis for the Syrian goddess, Atargatis.
Nowadays, Astarte is most commonly associated with Isis & Hathor from the Egyptian belief system and for the Graeco-Roman world Aphrodite, Juno and Artemis. Myself, I assimilate her most with Artemis. Mostly because she was seen as a warrior goddess by the Egyptians.
The connection with Venus is mostly due to one of the symbols used to represent Astarte, a star within a circle (indicating Venus). After all, 'men come from Mars, women come from Venus'! This does make sense as she was probably one of the chief deities for representing females during the period. But I'm not quite sure if they were the same goddess, as Venus had some different attributes- depending on your belief.
After typing all that, I see I have waffled around your question! Basically, she is not a demon.