I found an image I liked on Google Images of the green ninja and sized it to fit. (These are the same labels I used to create the favor bag stickers, only those were smaller.)
You could possibly even do this in a program like Picmonkey if you started with a blank sheet and added your image to it. You would just size your image to be 1600 pixels (width) by 500 pixels (height). This would give you a resolution of 200 dpi which should be sufficient for printing.
Just like the favor bag stickers, I had these printed on adhesive backed paper at Office Max. It was only a couple of dollars for all the sheets I needed. I would not have been able to buy sticker paper for as inexpensively as I had them printed. Plus, since these were so saturated with color, I didn't want to use all my printer ink from home.
Once home, I cut the labels out with my paper trimmer, removed the original labels off my water bottles and adhered on these stickers.
The bottles looked great on the food table and added one more element to tie the theme together. Little touches like this can be the key if you have to create your party from scratch and cannot buy pre-made decorations.
More Ninjago party posts: