Which sells on Zazzle, humour or image?

I have been adding products lately to my Zazzle store but I have begun to ask myself am I stopping people from buying my cards ( for example) by using messages which are examples of an off-beat humour? Should I simply leave cards blank, put images on t-shirts and leave these to sell the product. Does the average customer know that they can, or understand how to customise a product. I have decided to go for both angles. This means a little more work but should not be too ardous and if any products sell I might be able to answer this question. An example of my sense of humour:

past its prime by ArtyfaxCards
Create a notecard template at zazzle

The message inside reads:- Don't waste your time hanging around,
IT'S YOUR BIRTHDAY
make sure that you have a great time and enjoy yourself
from one old ruin to another My thinking was that the image is of a ruined pier, PAST IT's PRIME. Is this too obscure? I think that this also raises the question about getting thte card seen on google. Who searches for the specific text message? Decisions, decisions, I will be thinking about this long and hard. If I get to any conclusions then I will be coming back to report, LOL