This is a guy's way of turning you into an enabler of their perversion. IE: guys always have a very specific type of girl and fantasy in mind, but he wants to gateway you into it by having you pick you the chicks to photo first instead of him. Eventually, he'll start picking them. He just wants to break the ice with you on this new perversion, by making you feel like you have control over it.
Now, don't take all of that as me being judgemental. If you and he are into it, go for it. But, this sort of sounds like he's trying to gateway into inviting jailbaits into the bedroom, and trying to get you to slowly go along with it over time.
Look at it this way, today he's asking you to pick out the schoolies to photo. Tomorrow he's picking out the ones to photo. The next day he's asking if you want to go hit on one and bring one home. The next day, he's doing it himself. Before you know it, he's fucking schoolies behind your back. If you decide to put your foot down, he'll say "well, you didn't seem to have a problem with XYZ (previous activity), why such a huff now?!"
(I'm not saying every day things will get worse...I'm using "day" in the sense of "progression over a period of time")
In psychology the term is known as desensitization. EG: my psych book used a person with arachnaphobia as example... you make person see a picture of a spider and associate it with positive things ... nice music, good food ... an orgasm ... then you let them see a spider that's in an aquarium/cage while associating that event to something pleaseant, too. Eventually, you work up to having the person hold the spider, but since you keep associating something scary for them with something positive & nice, they slowly get desensitized to their fear.
Guys do this all the time to their gf's...or at least try to. They try to wear them down by talking about how great watching porn is, we should watch it together, we should watch it while fucking, hey we should maybe try soft-swapping with another couple and see how that goes, hey let's invite another girl into the bedroom ... slowly they try to get you to do more and more kinky shit.
If it's something you like, then go for it. You just have to communicate and make sure you're both on the same page. You have to make sure you'renot with a guy that's just seting you up to take advantage of your committment to him... ie: he eventually just starts fucking others behind your back.
Folks partake in poly, swinging, bdsm and tons of other kink while still keeping perfectly healthy relationships. How? Because they communicate, are open and honest with each other, and don't do shit behind each others backs.
If you're up for his fetish, then explore it. But, be warned that it may get him to start pushing your boundaries more and more. you'll need to be ready to put your foot down, not in a bitch fashion, but just tell him that he's reached a point where you can't condone supporting his fetish anymore. But, you may find that it leads to something really exciting and mind-blowing sexually for both of you. Never know.
