Here are a few ideas I found...
Using pages from an old book, or newspaper as the background or in specifics areas
I love the use of cardboard in this one; what a clever idea!
Different textures, using a variety of miscellaneous items from sponges, to bubble wrap.
All this makes me want to hit the thrift stores, craft isles, and sewing isles in search of goodies to use and supplies to buy!