There are lots of mistakes crafters make when selling online for the first time. However the biggest mistake I see made is not having high-quality images. Remember that people will not buy when they can't see very well. You should give you online shoppers a very good view of your work. I have even seen crafters who not only have great images of the front of their products, but of the back as well! Think about it, how many times do shoppers at shows pick up a piece and flip it over to see how the back is finished? Well, if people do this at shows, then why not give them that option when shopping on your site.