My 2 daughters did the BBB experience before we headed to NMSSHP. We did the $45.00 package (My girls just wore the princess costumes there and brought along the headpiece that they wanted to match their costume.) It took about 30 minutes. We did go after to get the pictures taken, but we just had thm added to our Photo Pass and got a chance to make our decision at home. Depending on your budget, you might want to consider buying a costume before heading to Disney. It really did save me big bucks and my girls didn't even notice. By the way, their are hair pieces, clips, etc. included in the package depending on which of the 3 hairsyles they choose. Also, the girls leave with a little "goodie" bag with their makeup, and either nail polish or an extra set of press on nails, depending on which the girl chooses. I actually would recommend against the press on nails, especially for the younger girls; they pop off very easily.
There is a thread on the Theme Park boards that includes many peoples pictures and videos. Try to check it out if you get a chance!
Pam