Paper was my first love. Plus it's plentiful and obtained freely.
Yesterday I bought a few discards from the children's section at the library to make envelopes. I've done this with magazine pages before, but the children's book pages are much sturdier.
(I don't mean to pick on Madonna again, but this is quite possibly the worst book I've ever read. Artwork is great though!)
I chose illustrations I liked and cut the pages to the same size.
Fold the bottom up and apply glue to make an envelope.
Trim the edges of the flap if you like. They'll need tape or glue later to seal.
I also decorated the interior flap of some plain white envelopes with smaller illustrations from the books.
I like them grouped together by theme; might make for some good gift giving.