General plugins

First, in response to Tom's old post above--the latest version sends, downloads, or saves the cert with the name of the certificate.

As for printing a mod name, you can do this by creating your own custom type. In the type certificate.php file, you could add your own custom lang string, and delete the string that prints the course name. You could change the code that prints the grade of the activity along with the name, e.g. if you chose to print the % grade for the activity, change this line:
$grade = $modinfo->name.' '.$strgrade.': '.$modinfo->percentage.'%';
to
$grade = $modinfo->name;

Then make the changes to the line:
cert_printtext(170, 420, 'C', 'Times', '', 10, utf8_decode($grade));

to change it to the correct placement, font size, etc.