Hook: Wall Large (Purple Rectangle)The Wall-Mounted Power Converter decoration fits into a large purple rectangle wall hook.
How to Get a Wall-Mounted Power Converter Decoration
Star Fortress Decorations
Star Fortresses are a type of solo or group content similar to flashpoints. You can not access Star Fortresses until you have completed Chapter 9 of Knights of the Fallen Empire (level 60+). The enemies in the Star Fortress have a chance of dropping bunch of different Star Fortress and Skytrooper Decorations, including the Wall-Mounted Power Converter decoration.
You can usually also find most Star Fortress decorations on the GTN, sold by other players who won them while doing a Star Fortress.