First, the picture answer - when you are editing your profile (My Home, edit personal information), look toward the bottom of the page and you'll see various options for an avatar. You can choose one of the stock ones, upload one, or link to one. If you need more help, just send me a PM!
The crabs come later in the game when the farmers learn new ways to get food. The villagers also feed themselves; you don't have to do that to keep them healthy.
