Welcome to Tamatalk. Hope you like it here. Thoses pictures are avatars. To get one go to setting a the top of the page then click on Edit Avatar. You can either chose one from the gallery or upload one from your computer.
Hiya! Welcome to TamaTalk, hope you enjoy it here.
Those stuff at the bottom are called "signatures", and no, you do not always have to type them. Go to Settings on the top bar, then go to Edit Signature.