I don't sell eggs or have any pictures of roadside stands, but I can tell you what I've seen that catches my eye.
The sign has to be big enough to see and read about what you're selling.
It needs to be perpendicular to the road, so people see it as they're driving.
Color catches the eye.
I don't know how people pay. Cash? You need to have change. Electronic? You need to have the popular apps. (I don't do any of them, so I don't know about them.)
In the winter, you have to protect the eggs from freezing. In the summer, you need to keep them cool.
Check any laws or regulations in your area for any restrictions.