There's a good article in The Wall Street Journal today about researching family photographs. It mentions Maureen Taylor, who is one of the best known genealogical photograph researchers and Colleen Fitzpatrick, who is now equally well known for her use of forensic techniques to analyze photographs. There is a link in the on-line article to a video featuring Colleen Fitzpatrick.
Maureen Taylor's columns are regularly featured in Family Tree magazine (the U.S. company) & photographs can be sent to her there for possible free analysis of costume, likely dates, etc. : http://www.familytreemagazine.com/photos/current.htm
Colleen Fitzpatrick, with Andy Yeiser, has a free weekly photo analysis quiz. It's well worth looking at the archived quizzes and participating regularly to sharpen your eye: http://www.forensicgenealogy.info/index.html
"The Photo Detective" , by Alexandra Alter, on-line & in print: http://online.wsj.com/article/SB119214969916756801.html?mod=todays_us_no