If it’s Avoda Zara then you may not sell them either! (Although, it definitely is not Avoda Zara, because nothing can be, inherently, an Avoda Zara. It might be Assur.)
Now that I checked up the Gamara and the Rambam, it does seem to be Assur. The Rambam makes it sound that a picture of the sun is worse than a person, for a person is Muttar to draw but not to make a statue while the sun and moon are not to be drawn on a panel, either.
However, there is nothing wrong with keeping it. You may even have a non-Jew make you one, as long as it’s not a 3 dimensional picture. I do remember seeing the definition that ItcheSrulik referred to, but it’s not in the Yad. The Gemara had a problem with the fact that Rabban Gamliel had a picture of the moon, and the only answer the Gamara liked was that it was made by a non-Jew.