I think I'm going to go back to an idea I had. How about my favorite quilt square. That is really easy and would make a sampler sort of quilt. I don't really want people to struggle over this, but I am having a hard time choosing.
My secret garden could just be things you would find in a garden...flowers, butterflies, a bird house, a play house, bird bath or small pond, different kinds of flowers, birds,
I actually have a secret garden made after my girlhood desire for a secret place to play.
I really think my favorite quilt block or pattern would be the easiest for everyone to do.