Imagedesc isn't too complex to include an example on-page. When you get to something like Template:Infobox_dkeyboard
, should it have an example of the whole template? Or just the most commonly-used fields?
I've always advocated copying and pasting code from existing pages as a syntax reference (which I still do), but this is a little less obvious with imagedesc. I only refer back to the template pages when I need to use a less-common parameter that isn't used in the page I'm copying from. (I just copy the infobox from the SIIG MiniTouch page each time, as it has the fields I need.)
I have at least since learnt that MediaWiki is intelligent enough to allow you to invoke a template on its own page; you just need to run ?action=purge once after each edit to break the dependency cycle and fully refresh the page. That's what I've been doing with the TODO templates — the example given recursively calls on itself to render the result, using careful use of <noinclude> and <includeonly>. Enough rope, but to your collective dismay, I've not hanged myself with it yet …
I've started writing actual documentation under Help, but whether it makes any sense to anyone or not, I don't know — writing documentation for a wide range of knowledge and experience levels is extremely difficult.