I think it's more common for people with this to cope by thinking in terms of abstractions, rather than the other way around.

The flag's a great example. Can't call up an image of a flag, but I can hold a kind of inferred 'essense' of a flag based on the abstract idea. Rectangle, some dividing lines depending on the country, kinda a wavy shader effect on the edges, probably a pole off to one side holding it up. But that's as rich as the image gets.

If internal monologue is supposed to be an actual voice that you perceive vividly then yeah, that's not present either.