You're right that there's more to it to build a full working implementation (including generating and sharing keys). I tried to show that by dissecting HTTPS (TLS): http://www.moserware.com/2009/06/first-few-milliseconds-of-h...

I didn't use stick figures in that post, but I used actual traffic with https://amazon.com. Amazon uses RC4, but could just as easily use AES.