For the icon tattoos, the largest tattoos are probably a bit over 2 inches long. The smallest about 3/4 of an inch long. There are some "bands" as well that maybe went up to 4 inches long. So all in all, there is a fair amount of variety as far as size, image, design. Obviously it's all in the same style.
I bought these as part my halloween costume this past year. They were a lot of fun to put on and wear around for the night. They start to come off pretty easily the next day with soap and water, but some portions were harder to remove and needed baby oil (or another shower). During the night that I was wearing them, though, they stayed on pretty well.
The only thing that I kind of disliked was that soon after I had applied the tattoos, my skin took on a very dry appearance where the tattoos had been applied, and it became apparent exactly where the tattoo outlines were. Applying lotion over them helped a lot. I haven't worn fake tattoos in a while though, so maybe it's a general problem for fake tattoos. Also, my skin is typically very dry already, so that might have contributed.
Kids would probably enjoy this a lot. The designs were a lot more intricate that typical "cartoon" tattoos.
The application technique is the same as usual (ie: place over skin, apply water to back, hold for 30 seconds, slowly peel off)