Sometimes I've had luck peeking at the image's EXIF data. I'm not an expert on it, but the EXIF data is like a hidden signature that contains info about the camera settings, date, photgrapher, studio, copyright, etc...
I had a photo I was trying to ID, general "Image Properties" gave me nothing helpful. I opened it in Photoshop and used File Info --> EXIF and it gave me all I needed to track it down and ID the babe. Unfortunately it often doesn't work because EXIF data may be stripped if the image is reformatted. But it's worth a shot. I'm sure there are plenty of apps for viewing EXIF data besides PS.