Wow, I had never thought of this. I'm assuming since our flower girls are ages 3, 5, and 7, that this makeup thing would be out of the question. And if their hair is combed neatly, that's enough for me, and I suspect my daughter, too. I think she's going to give them flowers to put in their hair. Knowing the values of the mother of the flower girls, I think this will be good.
This is such a good question that I haven’t even thought about. From a photography perspective I suppose it makes as much sense to put some blush and powder on the flower girls as it does on us, especially if you’ve got a pale little girl(I know some of the pictures from when I was little my face glowed because I was(am) so pale). I think it depends on how comfortable the parent and girl are but I don’t see any harm in some blush and maybe some sparkly lip gloss to make her feel like a little princess.
Also it might subtly gives the message that how they look isn't good enough. I raised a girl, and never suggested to her that how she looks needed augmenting. She naturally gravitated to makeup at around 14 without my influence.
My niece (age 10) is going to be a jr. bridesmaid, so I am paying to have her hair done (which is half of the price of a regular bridesmaid) and they will include her "makeup" for free. I'm assuming it's just a little blush and eyeshadow to make her feel special.
My flower girl however will not even be 2 years old yet. So no hair and definitely no make up. If anything, we will add a bow or headband.