All fields are optional. If nothing is entered anywhere you simply get a generic G33kFl33t badge.
Your name. Can be a real name or your online handle.
These two fields are linked. The QR Code will point to the
povided link. Besides a propper URL the link may also just be of
the form www.example.com (notice the lack of
http://) or mail@example.com (it will be
auto-completed to mailto:mail@example.com for the QR
code) or @twitteruser (it will be auto-completed to
http://twitter.com/twitteruser) or simple a
Twitch_username (it will be auto-completed to
http://twitch.tv/Twitch_username).
If the link field is not given the QR code will point to http://www.thegeekfleet.com/.
If the name field is not given the link field will be rendered as big as name field would otherwise be rendered. So if you just want to use you Twitch user name as your name but still provide the QR code link write it into the link field and nothing into the name field.
Choose the size of the printed badge. I found these sizes by googling for common badge sizes and measuring some old badge covers I had.
Note: It might still happen that your browser won't print the badge at the correct size. Make sure to deactivate any scaling options in the print dialog. Even then Safari under Mac OS X didn't print it at the exact correct size when I tried it, but Firefox did.
The dots (pixel) per inch.
When saving a PNG file this just results in a larger (higher resulution) image. There is no way in JavaScript to mark a generated PNG of a certain physical size. If you print it later you need to provide the correct physical size yourself.
When printing this should kinda control the DPI of the printed image, but only if the browser and printer driver also use the same DPI. This means if you provide a lower DPI value than the browser uses when printing the printout will be pixelated. If you provide a higher value the extra pixels are simply useless (but no harm done).
Show a gray border around the badge. This only really makes sense if the badge has a white background so you know where to cut the printout. It won't be contained in the generated PNG, though.
This badge generator was made by Mathias Panzenböck. The source can be found on GitHub. See also the TeamHooman Badge Generator.