What a fun picture of him! Wait til he's a teenager... LOL I'd probably crop it some (right side) to balance it.
I don't think it's inappropriate but if you put it 'out there' especially on a social networking site you never know who might find it and use it for, well I don't even want to imagine but unfortunately having worked w/young kids it seems necessary to keep in mind (odds are probably against anything happening but there's always a chance).
I know of someone who put their child's Halloween picture on their FB page and it went somewhat viral and she said at first it was fun and then it got creepy. And that was just a Halloween costume.