It does exactly what I needed. It sould be integrated in joomla core, as I don't understand what website could allow himself to use large image with small width and height attributes.

it's what I was looking for. I had to tweek it a little, cause the ugly table layout is not very css friendly. So I wrapped it into a div, removed the style attributes, and now, I'm able to easily change the apparence of the block.
But It would be nice to rewrite it table-less and standard-compliant.