I can't visualize every kind of object. The easiest things to visualize are simple geometric shapes with a strong color. By default, if I try to "visualize something" it will be a red triangle.
I cannot visualize faces whatsoever, even if the person is right in front of me and I close my eyes suddenly.
Glad it's not just me that cannot visualize faces whatsoever! But with the exception of faces, I can visualize complex 3d shapes if I'm lucid dreaming. When I'm fully awake, my visualization abilities decrease quite a bit, so when I get a chance (which isn't so often with kids) I'll often lie in bed for an hour or so just thinking visually. My wife thinks I'm being lazy, but it's often the most productive part of my day.
I cannot visualize faces whatsoever, even if the person is right in front of me and I close my eyes suddenly.