Fascinating responses. I myself typically use a combination of pictures and words. I will also argue verbally, 2 different points of view on a given topic. When reading or listening to books on tape, or even sometimes while watching movies, I will play movies in my head. However, there seems to be times that either I'm somehow thinking in feeling or spatially. It is difficult to describe. There are concepts that simply are. They are not words or images, but exist nonetheless. I say spatially because it seems like they have a place, but the image is blank, but the understanding is still there.
Interestingly, I asked an Economist professor how he thinks, and he said he thinks in words or math formulas!