I have a fresh Unity project, with just one 480x800 pixel image. It's platform is set to Android, and the aspect ratio in the game view is WVGA Portrait (480x800). However, the image doesn't occupy the whole screen.
The camera is orthographic, with a size of 5. My intention is to test different resolutions on the same device, and maybe test on other devices.
Why is the image appearing smaller, in the scene?
The project is set to 2D. I added the image firstly by pasting it directly to my Sprites folder using the Windows explorer, then by clicking Assets->Import New Asset, and got the same result. My only GameObject on scene is the one holding the image, this will be used as one of my game backgrounds.
Here are the texture import settings and the inspector for the GameObject:
I haven't tested anything regarding the UI on Unity yet, so no Canvas. My experience with the engine is two weeks.