Last night while working finishing up ME2, I made a trip to my cabin to swap out an armor mod, and it got me thinking: do all of the various collectibles in my cabin in ME2 make a reappearance in ME3? By collectibles, I mean my space hamster, my fish, my prothean relic, my N7 helmet, etc.
The ship models and hamster are all there, but you have to find them strewn about the ship.
Someone, Kelly Chambers I think, takes care of your fish for you. If you find her on the Citadel she gives them all back. Be careful as you have no one to feed them for you. You have the options of purchasing new ones if you want.
As for the orb,the helmet, and any other collectibles, they haven't shown up for me yet.