Custom Connect Screen
From Onset Developer Wiki
Since Onset 1.2.2 the client can display a web UI while connecting and downloading files from a server. The page to show is hosted on the game server directly and can be configured in the server_config.json. This feature is optional.
Put your html and other web files in the public_html folder of the server. If it does not exist, create the directory.
In your server_config.json configure the page that you want to be shown.
"connect_screen_url": "loadingscreen.html"
In this case it will display loadingscreen.html from your public_html folder.
To enable the cursor during the connect screen you can set the following:
"connect_screen_show_cursor": true
Example video showing a custom screen: https://www.youtube.com/watch?v=t-OYr2jkmfE