You'll have to use CSS to scale up existing avatars otherwise you'll need to adjust the thumbnail size parameters within CB > Configuration > Images, but it won't apply to the default avatar image that you're seeing and will only apply to new uploads. You can add your custom CSS to CBs built in CSS override functionality below.

www.joomlapolis.com/blog/kyle/18711-template-css-overrides-made-easy

As for adding more info simply edit your userlist within CB > List Management and under Columns you can add more fields to your columns as needed as long as the field is set to display on profile and published it should be available there.

I highly recommend reading the CB Primer Book for anyone new to CB. You can download it below.

www.joomlapolis.com/downloads/documents