Currently the piwik.php renders a 1*1 transparent GIF.
We could instead display a piwik logo that would help spread the word about Piwik.
The plugin would
* add logo field to site table in DB
* display logo at the end of log process
* provide an administration interface to show the different logos available and the user would choose one from them.
The logo would be on a per site basis ; you could display a logo for the site 1 but no logo for site 2 and 3.
there is no point doing it with the new piwik.js as there is no link back therefore the logo would not be linked