Here's a link to a site where you can design a box, print it, and fold it. Fun if you are really bored.
If you want to make an animal to go in the box click on this link: http://www.yamaha-motor.co.jp/global/entertainment/papercraft/animal-global/index.html
The picture is of an Okapi made with the pattern supplied on the web site.
There are many, many more things to make on Web Zen under the topic Paper Zen http://www.chaoskitty.com/webzen/archive.php?choice=74.08.08