Well, you got yourself into a corner with that vagueness, hard to place any significant characterization of the Scandinavian countries, like what flags to put on it if the region is technically a mix of 3 different countries. Well fortunately there could be few places where we could have all 3 flags placed together and still make sense and not be out of place.

Let's take the model us_flagpole (or ca_flagpole, it's the same) and modify the textures to include a unique flagpole model for Sweden, Denmark and Norway (if you're eager, nothing stops you from having Finland and Iceland too). Then we could arrange them in a set of 3 poles side by side (or 5) like seen at Bella Center in Kopenhaga
At places like the main garage and tunnel gateways

Additionally you could have a household pennants placed all over the Orestoke town, like seen here at Örnsköldsvik
It seems also that is common in both Sweden and Norway (not sure about the rest) to have a flagpole at each house to display a flag or pennant, you could reuse here the us_flag (or ca_flag) model

Perhaps anyone from Scandinavia would share an opinion whether such flag and pendant mixing would be a fair choice as you've decided to leave it vague for some reasons, so let's embrace it.