Everyone has encouraged me to brighten my photos and that has nearly doubled my sales. Also, the idea of doing something - even something small - EVERY day to move your shop along is great. In my case, it's usually making products and shipping out boxes, but on days when I'm not busy with that, I fine-tune my policies, brighten my photos, come up with new ideas, create treasuries, etc. Here are a few ideas for when you don't have a lot to do on your shop:
1) Make a treasury
2) Participate in teams
3) Switch out your featured items to maintain variety
4) Update quantities
5) Update your tags
6) Rearrange titles
7) Post on facebook/twitter/instagram
8) Write blog post
9) Brighten photos
10) Switch out banner
11) Create coupon code
12) Update shop announcement
13) Favorite some items
Each and every one of these helps, whether it is to encourage more sales, organize your shop, take advantage of social media, or help other shops out. By doing at least one every day, my shop is continually being improved!