According to Official Guinness Records,
The oldest obituary photo was that of Mary Leone Stephenson Reiss (b. Victoria, British Columbia, Canada, 15 March 1921, d. Sullivan, Indiana, USA, 16 May 2010), who passed away aged 89. Her obituary on 18 May 2010 in the "Sullivan (Indiana) Daily Times" included a photograph of her as a three-year old girl. That made her obituary photo 86 years old.
For a complete list of 2010 records, please visit 2010 Guinness Records in United States.