First, print out your images and cut them out.
Use laser or similar printer for this. I read that inkjet printers doesn't work for this.
I found out that printer paper works the best.

Also make sure you reverse all of the pictures and letters before printing out!

Roll out your polymer clay. Thicker clay is better to work with.

Put image of your choice onto clay.
You can also take colorful pictures, i just had black & white printer. ;) For better results of colorful images, take white clay.

Put really small amount of water onto paper.
Too much water makes next step harder.

Carefully start to rub off the paper with your finger. Do this carefully, making sure that picture doesn't moves or breaks. (excuse my English)

Keep rubbing the paper off. You can see the picture through the paper now.

Rub the paper off completely and the ink will remain on the clay.

Use napkin or piece of fabric to clean the excess paper off the clay. Also do this carefully.

Now you can cut your pendant to the shape you want if you didn't before. And attach eyepin,pendant bail or if it's thick enough, make a hole to make a bead.

After baking or boiling in hot water (i boiled),sand your pendant with sandpaper or nailfile if neccessary. Just don't sand the picture! You can also varnish your pendant.

Now your pendant(s) is ready to use! Enjoy! :)