Spiderlashes, I'm in my early 30's and no i dont think thats too prudish. If things progress with someone and you start a physical relationship with them, thats totally different than him sending you an almost crotch shot after 1 convo!
MY thought is, unless he's like 18, he knows that sending a pic like that indicates to a woman that he is interested in sex. But, I may be a little biased, I hate guys who freely post or distribute half naked photos of themselves. I dont like guys who are that self centered. I wouldnt bother talking to him about it....