So .. I would love to start a line of Mountain Curs [Seeing as I own one in RL]
Very few of the stock sites have any real great stock images - So I turned to one of my face book groups - and have several Images I personally am allowed to use ...

How do you credit a face book person though?
Just say "image provided from ___ on face book with special permission?"

Maybe "image provided by facebook.com/USERNAME" 

“Life is short but also like terribly and insufferably long at the same time.” - Jenna Marbles

I THINK it would be what vexation said and then the "used with permission"  

Hi loves! 

So, when you use a personal photo - you say something to the affect of "photo by skyler" or "skyler's personal photo" . 
So I feel that so long as you put that image provided by like Vexation said - I feel that is sufficient ! 

What vexation said!