When you get the photos from the security camera at Runciter's, be sure to examine them closely. Especially view I. It contains a good shot of Lucy's face and an ankle bracelet she's wearing.
Act II
When investigating the Eeisenduller murder, be sure to locate his dog's collar. The dog's name is Eisenduller's password to access files on his database.
Act III
When you acquire a photo from Izo's camera, notice the security camera on the wall above the China Bar. You need to ask the bartender to hand over the images.
Act IV
When you get to Lance and Luther's lab, check the monitors behind them. You'll find a file on Guzza.
Act V
There are two possible Early Q photos. You'll only receive one or the other. This depends on whether or not you find the scorpion box at the Peruvian Lady's. Whichever one you get, examine it before you head off to complete the game.