220 VAC Control Transformer "voltage on" indicator light.
I would like to know where to place an indicator light (what voltage, as well)


The voltage required is the voltage at that point in the circuit.


  ... for the incoming 220VAC, after the 2 pole circuit breaker? 


A good choice but if it doesn't light you'll need to check the breaker to see if that's the cause. You could add lights both sides of the breaker.


  The IEC Connector will provide 220VAC to the transformer, 120VAC to each leg, then the transformer will supply 120VAC to our equipment. 


Not the way it's wired in the schematic. Both 120 V windings are in parallel and will have 220 VAC applied to them resulting in smoke.

Remove H1-H3 and H2-H4 links and rewire with H2-H3 link.


  The 120VAC "Power On" indicator light is wired below the transformer. I am just having some issues with the 220 wiring. 


I reckon that that's all you really need. Transformer failure is relatively unlikely given the proper circuit breaker.


  Would a 220 VAC Panel Light illuminate, when wired across the two hot wires? (H1 and H4) 


Yes.


  Where would a neutral come from, if it at all needed?


The bulb knows nothing about neutral. It only knows about the voltage difference between the ends of the filament. If there is 220 V between the supply terminals then there will be 220 V across the lamp.