First thing to do is probably acquire the schematic Vid pointed you to and then check all of the output voltages at the power supply. If you're not getting the 100V high-voltage output you won't have any displays for sure. So first things first...
I may just not be able to see it in your photo, but is the ground wire attached to that screw post in the bottom of the backbox? There should be a wire attached there, usually with a wing nut. It has to be disconnected to remove the head, and is often forgotten when reassembling.
If you don't already know, be careful with the 2 big plugs where the backbox connects to the cabinet. On some machines, they are the same color and can be misconnected. Doing so will fry many things, so always verify the wire colors on both sides of each plug before you power on. On many machines one pair will be white and the other black, but not always, and I would verify wire colors anyway.
Good luck!
Dave