22.214.171.124 - - [29/Mar/2014:22:04:54 -0400] "GET http://ro2.biz/pixel.png HTTP/1.0" 200 151
But the most interesting part is that your apache is replying with "200", that is OK!
Nice catch! It's certainly a proxy.
See? The request asks for all the URL, http:// and host name included, just as if you were a proxy. The normal GET request for a web server asks only for the file part ("/pixel.png" in this case).
It's because of HTTP/1.0 protocol. Should the client use HTTP/1.1, it would look more usual.