There's no real "standard" to this... if everyone posted a pic of their rig, every single one would be so different.
At the most basic you need:
monitor of some sort/ if using an arcade monitor you need an iso transformer
Jamma harness
Power supply
Joystick
Buttons for the obvious, but also for a test button
Speaker if you want to test audio
Think of it this way- you need to build an arcade cabinet without a cabinet.
Some folks use small LCD displays. I myself use a 13" monitor I swapped out of a cab due to severe burn in, but good for testing pcb's.