Custom Xsession with Gnome visuals

I'm trying to create a kiosk PC only for web browsing using this tutorial as a reference (only difference - I'm using Firefox instead of Chromium)

It is working correctly in principle (only FF window opens when I log in using the Kiosk session) but it looks, well, super ugly. The scrollbar and right-click context menus look like from the 1990s - gray and boxy.

How could I modify the session to get Gnome-like scrollbars/menus without the whole Gnome desktop (top/bottom panel etc)?

My custom X session is currently set up like this:

/usr/share/xsessions/kiosk.desktop:

[Desktop Entry]
Encoding=UTF-8
Name=Kiosk Mode
Comment=Firefox Kiosk Mode
Exec=/usr/share/xsessions/ffKiosk.sh
Type=Application

/usr/share/xsessions/ffKiosk.sh:

#!/bin/bash
while true; do firefox -height 768 -width 1024; sleep 1s; done

Solution 1:

In /usr/share/xsessions/ffKiosk.sh:

#!/bin/bash
gnome-settings-daemon &
while true ; do firefox -height 768 -width 1024 ; sleep 1s ; done