Hook: Ship Hook (Giant Purple Square)The Derelict Spacecraft decoration fits into a ship hook (Nar Shaddaa, Tatooine and Yavin 4 only).
How to Get a Derelict Spacecraft Decoration
Cartel Pack Decorations
The Derelict Spacecraft decoration can be dropped from Scavenger Alliance Packs, which were released on the Cartel Market and bought with Cartel Coins. Cartel Packs, including the Scavenger Alliance Pack, include a random selection of items from the Scavenger Alliance collection of items. You aren't guaranteed to get a Derelict Spacecraft decoration from a Scavenger Alliance Pack, but it is one of the few ways to get a Derelict Spacecraft deco apart from buying it on the GTN from another player.
If you're looking to get a Derelict Spacecraft, the easiest way to get it is to head to the Galactic Trade Network (GTN) in SWTOR and buy it with credits from another player. If it's very rare and not available on the Cartel Market, you could try buying from the GTN and hope you get it.