The requisite image for all models and actors is a close-up head and shoulders portrait. Agencies and anyone casting, will not be impressed with anything too distracting or undiscernible. They're looking for an honest and clear image.
With applications of make-up, it's best to keep it light and natural, no sunglasses, hats, etc.
For attire, it's recommended to keep it simple, no busy patterns. Again, when someone looks at your headshot, we want their eyes to be drawn to you, not to what you're wearing.
Building your portfolio can be an entirely different process, and can include a number of creative images showcasing versatility and demostrating an ability to take on various roles and different looks.