Alexander Pope writes: "The sound must seem an echo to the sense". (
http://www.poemhunter.com/poem/sound-and-sense/) and Robert Frost talks of the "sound of sense". This makes me think that the problem of style and substance can be better viewed as how sound and sense relate in language. The style would be linked to the sound and the substance would be linked to sense, content, meaning or the intention of the words.
If one looks at it like that then sound and sense (style and substance) are different and they are different from what one finds in an image which might not have any intentionality associated with it.
In the case of Ecurb's example using Dickinson's poem, one can accept or reject the poem from two different perspectives. One can accept or reject the poem based on the metrical sounds that it uses, that is, one can judge it based on its style. One can also accept or reject the poem based on its theistic view, that is, the sense, content, or meaning underlying the poem.
Because of that I think style and substance (sound and sense) are different and perhaps peculiar to language.