Unity 2D Background Image Size

First off, I’d like to apologize if this has been posted before. I’ve been searching for the answer and I can’t seem to find the simple straight answer I’m looking/hoping for.

I’m making a simple 2D low resolution retroish game. I trying to create a background image for the game but I don’t know what size I should make it.

I want it to pretty much fit most screens when the phone/tablet is held vertically.

I’m stuck. Is there some sort of guide or something?

Thank you.

make it the biggest size possible…check out the Screen classes in the unity docs