I can tell you from real world experience that the stack is usually a combination of the following:
- Sponsors that aren't paying enough for larger branding on the car.
- Partners of the team.
- Suppliers of the team (which is why it's sometimes referred to as a supplier board).
- Driver's personal sponsors (sometimes).
- Sponsors who's branding isn't visible side-on.
If this is for your own from scratch livery then probably think of the following:
- Who's supplying the wheels.
- Who's providing garage tools.
- Who's the merchandising partner.
- Who's racewear & teamwear partners.
- Who's the IT partner/supplier.
- Who's the lubricants and fuels partner.