Embroidering Postcards

This is a sampler from an on-line class I'm taking from SF Center for the Book, taught by Hope Amico, a Portland book artist. I remember doing embroidery years and years ago, particularly a full length muslin caftan with an elaborate flower design on the front. I worked on it forever, and then never really liked it and sold it a garage sale. Hopefully a postcard-size object will be easier to finish. Take-aways so far: to make this work you have to punch holes in the paper, you have to be able to thread a needle, you have to have some amount of patience. Only one of the three does not present a problem for me. 
There is one more class. So far it's been fun, and the instructor has shown some fabulous slides of inspiring work. I do have some confusion with figuring out what should go on to the base image. The same thing happens with collaging photos. I tend to think of the image as a finished piece, already whole. The advice is always to just keep on layering, so I will. And then there's the age-old question: how do you know when to stop?