Pick out the best image of the birthday girl or boy for your note. Then pick any number of photo sites that allow you to customize the image and allow you to put text on the front. Upload and send off the image and within a week you should get your thank you cards back.
I’m pretty sure that this card was done on a MAC. If you don’t have a MAC, you could look into Shutterfly or a friend of mine does these with nice card stock. Her site is www.PaperRabbitDesigns.com. She will totally customize it to look exactly as you want it and then it comes out on a nice heavy card stock.
Bottom line, it’s always important to say thank you for coming to the party and for bringing a gift. My daughter is 7 and still remembers who gave her things over 2 years ago!