Best Answer - Chosen by the Asker
1) スス 2) ---ひゃい？ 3) ポツーン 4) もん 5) ぴゃ 6) ドッキィィ
1) 2) 4) 5) are not onomatopeias that commonly used. May be original creations of the writer. We need whole pictures to guess the meaning.
3) ポツーン lonely
6) ドッキィィ be surprised, astonished