Reviewing the documentation I found the following to resize and center an image:
((http://example.com/image.png width=500 align=center))
I used this a lot:
%(wacko wrapper=text wrapper_align=center)((http://example.com/image.png))%
the bad thing is that it is mandatory to use the size, that is I can't just center the image.
Is there another way to do it?