Intermittent Static / Garbage External Display On Wake and Boot? Picture included
If you look in the Console log you will find that the WindowServer is having a hard time finding the right protocol for your monitor.

Usually that happens when the hardware (cable/converter) connection are not stable, to long or near interference source.

From your picture it does look like your cable is to long and to close to the external monitor screen, and the Apple adapter is pulling its weight on to the plug.