When Ray (Colin Farrell) and Frank (Vince Vaughn) speak about the second house inside the bar, there is a sign for 'Lone Star Beer.' This is the beer that Rust Cohle (Matthew McConaughey) drinks in the first season.
Emily alludes to Woodrugh's time in the Iraq desert with an organization called "Black Mountain." This is an allusion to a private military organization called Blackwater, which had contracts all through Iraq and Afghanistan for security and special protective details. They normally employed only former Special Forces or Special Operations personnel, hinting that Woodrugh may have been Special Forces while he was active duty.
In the last scene, when Ray is searching the house, there is a book on the shelf about Nobuyoshi Araki who is famous for his nude photography.
For soap opera fans, you may also recognize Jon Lindstrom and Rick Springfield from the reoccurring characters they play on General Hospital.