The Kickstarter potion was intended to display the YOU ROCK message at the main menu so that part is probably already working for you.
I read in this thread that Kickstarter backers were supposed to get the trunks, the grail and the soundtrack from the Source Hunter DLC which should have been attached to our Steam accounts but Larian ran into trouble and it was still being sorted out. That was about a day ago and I haven't seen an update recently.
I'm not able to find any of the other Kickstarter rewards except for my adorable pet summon.
edit: My name isn't in the credits either.
I sent an email to Larian. I'm hoping they'll get to it in the next month
