Is it okay if I use that in a Workshop mod of mine?

This is so late [FaO] Carranty but in case you still hadn't figured it out:

When you hover over the icon, there are 3 vertical dots on the upper right corner. So while you are on the table you wish to play, click on that and select expand. It will then take you to a folder that has a single file that says custom border. After clicking that, that will set your desired background as your custom bg

i dont know

Nice. Took the liberty of using it in Mastermind Classic mod.

I subscribed to this, but the simulator doesn't seem to recognise it as a background. It is instead listed in the 'Games' section. How do I use this as a background with other games?