If you want something to frame, start with Fine Art. It is the museum look most people think of first.
If you want to laugh, try Silly, Vacation or Superhero. A hamster in a tiny cape never gets old.
For cozy gifts, Cozy and Holiday are warm and familiar. Retro is a fun throwback.
Because your first portrait is free in any theme and you can try others later, there is no wrong first choice.