Have you tried re-installing, or at least connecting, the original display? That would confirm if the issue is display or logic board related.
If the issue is logic board related, then closely inspect the connectors and the surrounding components. Look for damaged pins or missing or dislodged components. The screen you see shows that the LCD is being driven but the data is scrambled. That could be caused by missing filters on the data lines or something more severe at the CPU level.