What is a good theme to pick for an english project?

i have to pick 2 sonnets, 1 ode, 1 ballad, 3 songs, 1 epic, 1 childrens poem, and 1 limerick and they all have to be about the same theme and i can't think of a good theme to use.becuase i find a couple of poems for one poem and i can't find any for the other categories. plz help