The simpliest, and easiest, configuration on the badges is to change the background image (by default, it's a civicrm logo).
To do that, you simply have to set up a custom template directory, and add a logo (png format) in the directory templates/CRM/Event/Badge/CRM_Event_Badge_Logo.png or /CRM/Event/Badge/CRM_Event_Badge_NameTent.png (respectively for the Logo or name tent format).
You can also set a specific logo for a specific event by putting the logo into templates/CRM/Event/Badge/[event id]/[class name].png
eg for the Logo format of the event number 42, simply put the image templates/CRM/Event/Badge/42/CRM_Event_Badge_Logo.png
You might want to create a new format, simply go to the admin (http://sandbox.civicrm.org/civicrm/admin/options/event_badge?group=event_badge&reset=1) and create a new event badge.
You will have to provide a class that formats each badge. For instance, the Logo template CRM/Event/Badge/Logo.php contains two methods: the constuctor, that mostly sets the format of the page (how many badges per page), and generateLabels, that format each label.
$participant contains the datas about the participant (name, oganization, role...)
If you create a new format, please share it with the community and add it as a sub page below.
In theory, you can use a jpg or gif format. It did work much better with png in my case, YMMV.