I have no internal monologue unless I'm internally assembling bits of language for speech or writing (for example, putting my thoughts together for this sentence). If I get into a deep "flow state" while writing, or I'm in casual conversation with someone I'm comfortable with, that too goes away.

If I try to mentally visualize something I'm not looking at, even if I'm very familiar with it, it's usually impressionistic at best - rough outlines and swaths of color.