Traditionally in digital media, if you want to create the effect of writing on a torn-ioff piece of paper, you'd create a <div> element with an image or border image set.
I recently came across this:
http://tex.stackexchange.com/questions/86372/torn-paper-matching-up-the-torn-edges
It appears that in at least one programming language, it is possible to algorithmically define ripped paper effects. Does dokuwiki have any support for this sort of thing? Is it possible to adapt the code from there into something dokuwiki can use?