Having a big collection of pets for LU 2 is what!! So how do we do it I hear you ask? 1:(optional) Make some concept art or a picture of an animal you think would be cool, then upload the concept to the Wiki. 2: Make it in Lego Digital Designer and upload a pic here, and upload the file to the Creation Lab!
Oh, by the way, here is a list of animals that were in the origional LU, so you know what the pets need to look like, and you also know not to use any of those animals (unless you want to)... http://legouniverse.wikia.com/wiki/Pets
Snow Wolf - Nando248
Squirrel - Goggles99
space bot - Jamt2
Blactron Robo-Dog - Brickenneer (lfx. file)