You can get Blackmail Photos in one of three ways:
Loot.
By asking your mafia to send them to you. BUT how does each member send them? Where are they?
Do you mean "Blackmail" Photographs?
You get the "Cooked Book" from the "Blackmail a Track Official" in Region 4 Milano in Mafia Wars Italy.
Obtain Compromising Photos.
Under Hitman - Obtain Comprimising Photos
You have to do the Hitman Job called Obtaining Compromising Photos.
Defeat one the mob bosses
They're used as consumable items in later job tiers.
You can get BLACKMAIL PHOTOS on New York Hitman Tier: Obtain Compromising Photos. Check out my related links for MAfia Wars Updates
Those are usually used for special missions or just for collections.
you will need approximately 368 Blackmail Photos to complete the Boss job tier.