This might be controversial. I know it's up to every author/publisher but I've been reading a poetry collection that has full page, full colour illustrations.
Now, I will say right off the bat that I'm not an artist. I might think a drawing is pretty but I don't see the artistic craft that goes into it. And if I'm honest, I'd probably be more interested if a book was illustrated by the author themselves.
However, on the whole, I find illustrations a bit distracting. Maybe it's because, as I said, I'm not artistically inclined or because I haven't read books with pictures for quite a long time. I just wondered what other people thought.
(For simplicity's sake, I will refer to illustrations/images/photographs collectively as 'images').
Great question... though images are definitely not a requisite for poetry, I personally think they have a place in poetry provided:
The poem stands perfectly well on its own, and the image is not there to provide further elaboration on the poem's meaning. The poem should communicate that itself, as poems are intended to do.
If it is explicitly clear that the image is only there to accompany the poem. By this I mean, is secondary to whatever is being expressed in the poem without influencing or altering the main messages/meanings of the poem. The image can add to the message in the poem, but only as an extra or alternate reading (as opposed to significantly impacting the meaning/s of the poem... if that makes any sense!)
The image needs to reflect exactly what is going on in the poem and should not provide extra 'clues' to the reader. Again, all messages must be clearly and definitively communicated via the poem itself.
I will say, like Lana's 'Violet', sometimes poems that are accompanied by photos of locations significant to the poem or the poet enhances the reader's connection with the poem. However, like point 1., the visual descriptions of the location featured in the poem must be sufficiently communicated via the poem itself. Das just my two-cents.