''Little one, / whoever you are, / wherever you are, / there are little ones / just like you / all over the world.'' So begins the Australian author Mem Fox's joyful picture book ''Whoever You Are,'' a celebration of the world's diverse cultures, both our similarities and differences. Leslie Straub's innovative, colorful, folk art-style oil paintings of children from all corners of the globe are bordered with photographs of hand-carved, bejeweled frames--and they all reflect Fox's message that no matter where we come from, within our hearts ''Joys are the same, / and love is the same. / Pain is the same, / and blood is the same.'' A gem!