If you are curious how difficult it will be to add items to Starbound after launch a recent update from Starbound developer Mollygos should interest you. Outlining the step to easily create in game items I am thinking of a few I would like to add to the game when it ships. Like a placable Cheerful Ghost framed portrait for starters :D

Tiy also posted a few short blog posts about the new stuff that was added to the game last week as well and I have them linked below for your enjoyment.

http://community.playstarbound.com/index.php?threads/basic-object-implementation-a-tutorial.21463/
http://playstarbound.com/a-brief-look-at-what-weve-been-working-on-this-week/
http://playstarbound.com/10th-may-progress/