I had an idea for a new hat design the other day as well, so that will likely be on my plate soon. And I have another hat that I made pieces for, but haven't finished. This is mainly because I need to do some embroidery to finish it, and embroidery is one of those things that I've always had trouble getting into. Cross stitch is fine because there are designated places to put the stitches. Embroidering with no lines to follow is a recipe for disaster for me. This is why I paid to have "Police Box" machine stitched onto felt for my TARDISes. :)
So we'll see how successfully I can do the embroidery. If it is too fussy for me, then I might just write up the pattern and sell that rather than making the hat as a regular item for me shop. I like making hats, but if I find that a hat is really fussy for me to make, it becomes a lot less fun for me.