Boxwood and yews, though perhaps overused, are great for heavy shade and even do well in containers. Make sure you rotate them so all sides get what little light there is. Also, don't forget to occasionally water the pot, even in winter. Evergreens especially need water in winter. There are other good shady annuals too.
Caladiums are good and colorful.
Torenia, and of course, ivy. The ivy is a perennial though. Make sure it stays in the pot as it can be invasive. I have way too many of them. I've tried digging them out but invariably miss a tiny seedling.