Personally I'd say that if you don't know what state your texture is in, there's a logic error in your code.
A texture "holds" an image if you have loaded one and it doesn't hold an image if you didn't load an image or if the loading failed. So the states are pretty clear and can easily be kept track of.
If you really need something like that, I think you can check the size and if it's zero, the texture doesn't reference an image.