I'm not sure that teaching from the back of the book is such a good idea.
Textbooks follow a logical pattern of skills that build on each other.
By starting at the back of the textbook and teaching forward that hierarchy of skills would be abandoned. I don't know if that would be beneficial to your students to teach in that way. If you want some new ideas of how to teach math there are many really good ideas in various books, just go to your library or get some ideas from the Web. There are also lots of good children's literature available to incorporate into your lessons. Seek out new and interesting ways to teach old ideas and skills.