Marketing can be hard - what I do on my FB fan page is when I post a pic of a new item, I link it directly to the listing in my Storenvy store - that helps drive traffic to the item in my shop, so if they see it, love it, they can click the link and go right to it, and I'm not spamming. So whenever you add a folder of new stuff to FB, add links so people can purchase them right beneath. It works well for me!