When it comes to postcard printing there is a lot that you need to think about. Before all else, what type of images are you going to use? Adding a photograph to a postcard is a great idea, but only if you move through the preparation process first.

It is essential to choose a photograph of high quality. If you don’t do this you should expect the final result to be less than desirable.

Moving on, you have to use high resolution originals. With postcard printing this is mandatory if you want to be satisfied. If low resolution images are used, the postcards will end up fuzzy and grainy.

Finally, make sure you preview the proof before printing. This will give you a good idea of what the quality will be, as well as the overall design.

Adding a photograph to a postcard can be simple if you take the right steps.

source:  http://www.contentcaboodle.com/business/marketing/how-to-prepare-photographs-for-postcards.html