Rhyming pbs usually tell a story. The poems Bill referenced, Casey at the Bat and Twas the Night Before Christmas (and Edward Lear's The Owl and the Pussycat) all convey a full story. Andrew Clements's recent book, Dogku, tells one unified story through interlocking haiku -- it's sold with the picture books, not the poetry books. Jack Prelutsky's collection of individual haikus, If Not for the Cat, was a collection of individual poems, not a unified story. It is stocked with the poetry books.
A poetry collection is a collection of poems, not a rhyming (or free verse) poem that tells a single story. Collecting up enough poems to fill a picture book doesn't make it a picture book text -- it'd still be a poetry collection of individual poems.
Fuzzier would be something like Carole Boston Weatherfor'ds Dear Mr. Rosenwald, which is in free verse, in individual poems, which when read together, tell a complete story. I could argue for having a crit group look at that, if the "rules" are picture books only. But probably not individual poems which couldn't be their own book.