I've never been to an atheist one. There were lots of people who never attended or seemed religious but the service was always held in a church. There was one case where a church refused to have funeral service of one guy and the family had to make arrangements with another church.
If I can plan my funeral. Beer and snacks. Some nice words about how awesome life is. Touching song. Would like my ashes to be buried with a tree planted on top. Perhaps a "grave stone" with a cryptic set of clues to keep treasure hunters and conspiracy theories busy for centuries