I see three possible nice backgrounds for a service designer:
1. Design background
If you have a background in graphic design, UX design or product design you already know much of the tools that Service Designers use. You’ll maybe miss the consultant part of the service designer but the transition from being a designer to service designer is pretty natural.
That’s the background I had before turning towards Service Design.
2. Psychology or social sciences background
If you have a background in psychology you’ll have a great understanding of the human mind, what influences human behavior and how to better understand fears, beliefs and motivations of users.
The difficult part here will be to transition from an academic perspective to a more “get shit done” mindset. But if you have a psychology background you’ll have some great tools that you can bring in your service design career.
3. Business consultancy background
If you have a background in business consultancy, then you’ll already have the mindset of the consultant. You’ll then only have to learn the special ways service designers think.