Onomatopoeia is not a form of poetry, it is a literary device. Onomatopoeia is the name for the use of words to represent specific sounds, such as "Vrroom" for a car revving, or "Bang!" for a gunshot.
I was told by my English teacher that there are no rules or limits to a concrete poem but on the internet it said it was a shape poem! Anyhow, I don't think there's a rule for how many lines the poem...
There's no minimum and no maximum. A one-line poem is hard to imagine, but not impossible. An epic poem could be very, very long. Certain verse forms do have fixed lengths; for example, a sonnet is...