I’ve been knocked-back before, for pics that I thought should be fine. According to the rules, they may pull you up for:
Too much shadow.
Background not plain/flat.
Head slightly tilted.
Having said that, the concept of baby passport photos is a bit flawed. I have a 6 month old and his passport shows him at 3 months: he’ll still have it when he’s a 5 year old schoolboy… Probably totally useless as a form of recognition by then.
Good pic by any other standard though. Your boy looks cool.