Hi, no you don't have to know any HTML to use Auctiva.
I'm not sure what you mean if it will automatically update your pics, do you mean like when an auction ends or starts, if the pic will be automatically added or removed? If so, yes, everything is automatic.
A link in your sig? Click the "Auctiva Community" link at the top of the forums. Then click Personal Zone, then click View/Edit Complete Profile. Scroll down and you'll find the place for a signature.