Epicurus’ Letter to Herodotus and especially Lucretius' account of eidola in De Rerum Natura IV reveal that the school explained these various mental phenomena by analogy with sense perception: our mind is impacted by special, particularly thin and fine eidola, which in turn form the basis of our thoughts and dreams.
(that's a quote from the article) -- And so to be clear, my objection is not that images can't and don't spur thoughts, my objection is to jumping to the conclusion that images are the SOLE basis for thoughts and dreams. Just like I can see a tree in front of me and choose to contemplate it or think about something else, or hear a symphony and choose to think about something else, there seems to me to be no reason whatsoever to conclude that the mind's reception of an image would dictate that the mind occupy itself in contemplating that image to the exclusion of other thoughts.
I would also add "no reason whatsoever...." especially since we know that Epicurus considered agency to be an important attribute of human action - it would fly in the face of agency to presume that receipt of an image would compel the mind to pursue that image and nothing else -- any more than we should consider hearing or seeing something to compel our thoughts to comply with what we see or hear.
At least in my own case i think it is pretty easy to stare into space with eyes wide open, presumably seeing what is there to be seen, while my mind is off in a direction absolutely unrelated to what is in front of my eyes.
Maybe i should also consider the example that my wife frequently tells me that regardless of what i am hearing, I am sometimes / often oblivious to the words!