Cutom GUI on WisGate OS

Hi everyone,
I’m testing a bunch of RAK7249 Gateways running “WisGateOS_1.1.1_RAK_20210712162902” release.
As stated on a RAK press release article:
For the fans of personalized software, we’ve implemented the option to change the logo and the color scheme of the Graphic User Interface (GUI). Match WisGateOS with your company colors and vision and make it your own!”, there would be the possibility of customizing the GUI of the gateway, but I can’t find any guide or tutorial.
Can you help me?
Thank you in advance