Different post type, different markup

Not exactly what I’m looking for, it basically just changes the style by applying a class onto a post. I’m developing my theme in html 5.

A normal blog post would look like:

<article>
  ...
</article>

A post with just image would look like:

<figure>
...
</figure>

A post for poems would be:

blockquote
...
/blockquote

And so on… Any idea how?