Motherboard bios question

The BIOS is what talks to the hardware so you can run software i.e. an operating system. With no BIOS the computer will do nothing as it knows nothing about the hardware and cant interface with various things like the CPU or graphics card. Your specific question, whatever the screen shows when it is powered on but inst hooked up to a computer would be what it shows when you have no BIOS as it will effectively be the same and for most monitors yes this would just be a black screen.