I used to design and sell greetings cards on sites like Zazzle, it all started off failry well. You'd be amazed at some of the occasions people will buy cards for - for example:
Yup, people will buy cards for folks who have just passed their driving test. It actually sold reasonably well, it still sells from time to time now about 5 years later.
One of the best sellers I had was a christmas card called yellow snow
Every year around Christmas I'll receive an email telling me a bunch of these cards were sold. Just thought I'd share them, I thnk they say a lot about me and my personality.
I couldn't take it seriously, in the end I submitted a design with Rudolph abusing cocaine and offering it as an explanation as to why his nose was red - the design was rejected.
The final straw was when I submitted an image clearly lampooning Adolf Hitler (He was depicted as a clown in an image entitled "ein Klown") which I wanted printed on a mug for personal use. The design again was rejected and I stopped submitting new designs after that.
Maybe one day I'll upload those images - scared I'll get into trouble!