Here are some suggested route marker signs for Virginia. The present State Primary route markers are a kind of rounded shield in a black square, and the State Secondary is the boring circle sign.
Here's the present Primary route marker.
(Grey represents sky, which is typical throughout)
This one can be for limited-access free roads like Quebec's Autoroutes.
This one can be for toll roads.
This one can be for the Primary roads.
And this one can be for Secondaries.