Just want you to know 100 is not necessarily the magic number. Whatever number you're at right now could be magic if you convince it so. I hit the 100 listing last week. Sales still sporadic. So give you best, whatever number you at right now make it works. Not much help here but now you know to take it easy about the number.
When you see someone (in your field) is selling their stuffs like hotcakes. Pause and study why are they having that many sales. I look at your store, they look great. However I don't have discerning eyes when it come to custom logo design. So you've got to study what the tops seller are doing that make them to the top, so to speak. It's not just the design, but what behind it that make them great. The essences, the behind the scene, the between the lines. If you daring enough, ask them :-).
Hang in there & All the best