1. I love picnik! get a membership (I have a premium one but I do believe you can do everything for this invitation with a free membership). If you don't have picnik, you need a photo editing program that has a doodle and text tool (pretty much all the basic programs do).
2. upload any photo into picnik and go to the doodle tool, color everything white so you have a clean slate to work with.
3. I used the doodle tool to draw the ice cream cone on the computer, free hand. It took a few tries and a lot of undoing and redoing but eventually I came up with this shape.
4. Last I just added the text into it. This whole thing was so simple and I'm pretty pleased with it.
(if you want to take my design and try to play around with it or clone and change words if you know how to do that, that's just fine! just give me credit for the design if you post it or anything. I'd love to see what you created so please show me!)