Regarding imagery as exciting, a poem by Carl Sandburg entitled "Jazz Fantasia" comes to mind. Here is the third stanza of this poem:
Moan like an autumn wind high in the lonesome treetops,
moan soft like you wanted somebody terrible, cry like a
racing car slipping away from a motorcycle cop,
bang-bang! you jazzmen, bang altogether drums, traps,
banjoes, horns, tin cans--make two people fight on the
top of a stairway and scratch each other's eyes in a
clinch[embrace] tumbling down the stairs.
This stanza that contains auditory and visual imagery is certainly replete with images that excite the senses. And, it underlines the meaning of the quotation that here it is indispensable in this poem to the description of the jazz players, whose rendition is exciting.
However, there are other poems that employ imagery for various reasons other than to be exciting to the reader. The imagery may employ visual imagery in order to depict the grave, as Emily Dickinson does in "Because I could not stop for Death." Nevertheless, while not being exciting, the imagery can still excite the senses. That is, the imagery stimulates, or arouses the senses towards sorrow, empathy, etc.
The idea behind the statement is quite strong. Yet, I think that the wording of it is a bit awkward for my tastes. In my mind, imagery or mental pictures created through a poem is indispensable. Yet, I am not sure I would consider these powerful elements as "exciting," per se. Some of the most powerful images are not necessarily exciting ones, but sad, anxious, melancholic, or even redemptive one. For example, Yeats' use of imagery in his poem, "The Second Coming," is a use that does not aim for exciting as much as they are foreboding, tragic, and ultimately sad. When Wordsworth or Keats expand their views on the role of the subjective experience in the natural world, it is redemptive. Each of these instances feature a powerful use of imagery to help bring out the meaning in the works. Exciting might be present, but in the end, there is an emotional experience that I don't feel is exciting, as much as rich or powerful, or even contemplative. The second level of analysis that is present would be the second half of the statement. The definition of an "exciting life" is a challenging one. To reduce it in presuming that action and emotions must be present might not be as effective as leaving it wide open. There are many who live an "exciting" life that might not possess much in way of action. I think that to make such a call seems to presume quite a great deal.