Burial grounds in the U.S. are a mixed bag. Depending on the part of the country you are in, they can take different forms. For places like Louisiana where the water table is high, they are above ground. For places like New England where long ago prior to construction equipment, they had crypts to place the bodies in until spring. Many cemeteries are online at the international FindAGrave.com. However, not all have headstone photos and not all have photos period. This site is still a great resource to find the locations of cemeteries by state/county and even town or city. BillionGraves.com is another international resource many people find handy, although unfortunately for one-place studiers you can't search by place alone (there is a trick through - once you've located one gravestone in your place you can click to view all the images from that cemetery). In addition, Google Maps marks out cemeteries on their maps as well.
Seek out books akin to David Lambert's Massachusetts Cemeteries to find those small unknown cemeteries that may be in the woods in someone's yard. There are plenty of them around. In the South, there may be burial grounds on private property from an old farm that existed long ago. The local church or public library would be a good place to email or call if you get stuck.
In the UK, Deceased Online is the largest standalone site of burial records, and regional family history societies may have mapped, photographed and transcribed particular parish graveyards. Be sure to visit your long-deceased OPS residents in their resting ground, and photograph and transcribe their gravestone before time beats you to it.
Christine Sharbrough and Alex Coles