The very first visual image Edwards uses is found in the title: “Sinners in the Hands of an Angry God.” Think about the differences in size this image indicates: we sinners are tiny enough to fit in God’s hands. That image should provide humility and perhaps fear in the audience/reader.
There’s another visual image before the body of the work starts, found in a biblical quotation: “Their foot shall slide in due time.” While that might make some fear as well, my main emotional response is anticipation and curiosity: why will they (whoever they are) lose their balance?
And if you want the first image in the body of the work, that is found in the first few paragraphs, in the explanation of that likelihood to fall, with related verses. Here the anticipation moves to foreboding: something bad is going to happen.