Help:Long parameter demo
This is the result of calling Template:P1 se with a parameter value that is a long string of wikitext, look in the edit box, and see the opening braces a little below, and the closing braces at the end. It is a copy of part of Help:Images and other uploaded files with the template calls and a separate pipe in nowiki tags. It demonstrates that a parameter value can have (the wikitext for) sections, links, and images.