There will be a lot more documentation coming to help you create a BuddyPress member theme. Right now, the best thing to do is download the “Skeleton Member Theme”. This will give you a solid base to work on when creating a new theme.
The skeleton theme contains all of the base template files, which include all the template function calls you need, plus a set of CSS outline files for you
to work from.
I’ve taken a look at the theme source files and Andy has done a great job of offering up a clean base to start from. All you have to do is use your creativity and plug in the values for the CSS provided and off you go! Note that this Skeleton theme is aimed at theme developers and is not actually a user selectable member theme.
Snippet of code taken from the Base CSS file.