Show him how cute the little naked pictures are & that her bits are hidden. Maybe he'll think it's cute too ;)
I'm a photographer as well and the best newborn pics are the nakey ones.....for lil girls we add butterfly wings or angel wings for boys. Or on an old fashioned scale..there are lots of ideas...lots of ideas all nakey pics are with parts covered except bum. You.can Google newborn photography and get ideas :-)
The photographer I'm going to does that a LOT, and I think it's so cute, BUT she's got a very over protective daddy, haha! I picked out an outfit with just a pettiskirt bottom and headband and he said where is her shirt?!? (like she's got anything to show off!) If I can't find anything else I think that might be what we have to do!
This won't help for outfits, but the cutest newborn photos I've seen recently are when they are naked & situated where their bits aren't showing. I can give you a site of a photographer I know that does the most darling newborn photos to give you some ideas.