Use them as an inspirational tool for students to either write a story that they imagine from the pictures or tell may tell the story orally.
Since the students create the story, the same book can be used at any level of English skill. If the book has a theme, perhaps a picture book of a holiday like Christmas or Valentine's Day, the class can be given background information and vocabulary on the subject matter first, then either individually or as a group activity, they write/tell a story. The picture book serves as a "cue" when story telling. Wordless book will get students thinking in English and engaged in using the language.
Here is a link to a list of books categorized by types such as holidays, animals, fantasy, etc.