Here's some technical tips for those that are interested:
• The overall measurement of the art should be square.• I started with 16" square art and resolution of 150dpi. I added an extra inch around the outside for wrapping around the sides, which made the final 18" x 18".
The MiDesign site helps you try out your art and even preview exactly the way it is going to look before you pay for it. Now I just have to figure out where to hang my masterpiece. Thanks Michaels!