I can't see a mechanism for DVI signaling to make that pattern.
So either a backlight is arcing to something, or maybe the
power supply inside the monitor is the problem.
The power board on the X223H is on PDF page 39 here. The power board has
the AC input power connector, and makes low voltage DC for the logic.
But it also has the transformer and four high voltage connectors for
the (capacitively coupled) CCFL backlights.
http://support.acer.com/acerpanam/Manuals/acer/2010/ServiceGuides/SG_X233H.pdf
Many monitors of various brands, have had trouble with swollen capacitors.
The components with the "X" stamped in the top, are electrolytic
capacitors. If the top begins to bulge outwards, it means gas pressure
is building inside the capacitor. The "X" in the aluminum casing, is
for pressure relief so the capacitor will not explode. This releases
the pressure, in a safer manner.
You could try visual inspection of that components.
In terms of the backlights, any foil materials, insulation and the
like, must be put back exactly as you found it. As the electric field
around the high voltage circuitry, is all considered a (stray) part
of the electrical circuit.
The small blue capacitors near each of the four backlight connectors,
are coupling capacitors. They have values measured in pF, as in 22pF
or 15pF or so. Waving your hand around the area of the PCB, is a couple
of picofarads as well. This is why the backlight circuit is sensitive
to capacitive loading (foils, insulators etc). It's because any
stray capacitance in the circuit, takes on a significant value
when compared to the 15pF or 22pF or so which is in series with
each CCFL output. The capacitor is used, because the CCFL tube
is not allowed to have any DC voltage on it. It would degrade
the electrodes inside the tube.
Paul