LVDS display troubleshooting
Can a LVDS generally produce a "rather" correct image using this kind of wiring? Or is a LVDS twisted-pair connection mandatory?


I don't know your pixel clock, but


  The prototype connects the LVDS […] using free-floating enameled copper wire.


sounds bad.

The whole idea of LVDS is that it's differential and hence the routing can take advantage of the electrical field wave traveling between the conductors of a pair.

High-speed LVDS interfaces define a transmission line wave impedance (typical values are around 75 to 100 Ω), and your transmission line has to fulfill that. Your wires certainly don't.

Even without that consideration: Pixel clocks are typically in the high MHz range. You wouldn't ever want to do that with free-floating wire, because that becomes an antenna / filter / otherwise completely undesirable.


  I have tried to visualize the LVDS signals using an oscilloscope, with no success. How can LVDS signals be best measured using an oscilloscope?


Rather easily? Simply use two probes and use your scope's ability to calculate the signal difference on the fly, or just use the two probes and do that yourself visually. You should be able with a bit of practice to get a useful eye diagram. Of course, not on the far end of free-flying wire...