It depends. If I spend a week looking at elephant heads, I'll see them even if I don't want to. I have this problem any time I get really into a video game.

I forget the name, but there was a free to play Starcraft clone/homage I got hooked on. After a while, entire scenes would play out in my vision when I wasn't focusing on anything. Doesn't seem to happen as much these days, but I also have a healthier relationship with my hobbies.

This also happens with (fiction) books to some extent.

Not being able to visualize stuff hasn't been an impediment to visual art. On the flip side, being able to compose entire songs in my head hasn't been a benefit to making music: it collapses on contact with reality.