Greyback:
Having failed with Malfoy's prissy wife, he has hopes for Bellatrix. He finds her air of barely controlled violence erotic.
He was scared of the dark as a child.
He doesn't like cats. Dogs are tastier and easier to catch.
Muggle automobiles disturb him, especially the ones they call 'lorries'. He has an urge to chase them he can neither explain nor rid himself of.
He thinks his new scars rather rakish.
Wormtail:
He rather admires Snape. When James and Sirius teased Snape, Snape fought back. When James and Sirius teased him, he started following them around and doing things for them so they'd like him. The plan failed.
He misses the Weasleys. Being their rat was the time in his life he felt most loved.
Of all the pleasures of life, he really believes that a gentle scratch on the ears is the best. A good crumb of Stilton is very nice, too.
House elves hate him for no reason he can name. He finds them eerie, so it all evens out.
He's become convinced that Nagini comes up behind him and trips him on purpose. He's right.