The place I’ve gotten the most from sales of my artwork on is cafepress.
When my son was a baby I did it full time. The company I was a partner in collapsed while I was on an extended maternity leave and getting a new outside the house job with a new baby seemed complicated, so I liked that I could do cafepress completely from home. I also did zazzle and threadless, but niether of them paid off like cafepress. After a couple of years I was making enough to pay for all the Christmas gifts. I was doing well enough that I was actually paying for advertising on other sites.
Then one day cafepress got greedy and started screwing over the artists. First they stopped paying commissions on traffic brought to cafepress. Then they took away quantity bonuses. Then they stopped letting designers set their own prices in the market place, which was my final straw. I pulled all my good things and left up a few basic thing that had taken me just seconds to make on illustrator. I have been making a wee bit from those.
Lately, I’ve been too sick to really work again, so I have been going back to it, even though I am not at all happy with cafepresses policies.