The fact that you've been together for two years, but you still think this could be 'a test' and that he might 'judge you' for it, suggests to me that this relationship is absolutely not healthy enough for you to consider sending him a nude picture.
You've been together two years, but the way you're talking about the possibility of him testing you and then judging you for falling into his weird 'send nudes' trap sounds like something a woman would say about a man she'd only been on a couple of dates with. Is this some sort of long distance relationship or something? How well do you actually know each other?
It's pretty obvious that you're not actually comfortable with this and you shouldn't do anything you're not comfortable with for anyone.
While I think the OP specifically would be be unwise to send a nude pic - in general, I don't really share the general Mumsnet horror of exchanging pictures with a significant other, if both partners find it sexy. Obviously there is a risk that they might end up being shared, particularly if the relationship breaks down, but I think if someone is aware of that risk and feels that the fun outweighs it, then it's fine.
Plus... You know he only wants it for one purpose, and it's not a purpose I'd be keen to facilitate - why would I want him to be using a pic rather than connecting with me in person....
Well, it wouldn't be 'instead of connecting in person', would it? It would be 'in addition to connecting in person' or 'for those occasions when connecting in person isn't possible due to distance'. It's OK for anyone to enjoy a wank as well as sex, you know.
At the very least he'll probably have a wk over it 🤢
Why does he want it, do you require a dick pick? Thought not.
I don't understand why you'd consider it repulsive that a man would be turned on by a picture of his own partner, or why you'd think it was impossible that a woman could be turned on by her boyfriend's hard-on.