Webconverger has its own Firefox kiosk extension to tweak the user interface elements such as the URL bar and icons.
Default
chrome=webconverger
The goal with this default to have a stable, simple & familiar user interface for using the Web.
No address bar
chrome=webcnoaddressbar
Customization option, perfect for filtered setups. For customers who want patrons to browse, but not enter in URLs to navigate away.
Fullscreen
chrome=webcfullscreen
Customization option. For customers who want to do basic Digital signage or just show off some pictures somewhere.
Neon has further tweaks and currently proprietary extension for the digital signage use case.
If you're concerned about the scroll bar, alter the overflow CSS element.