The standard Internet Sales solution delivered by SAP comes in 2 flavours so that it can be run on either CRM or just R/3 - certainly this was the case with version 4.0 and I assume it is still the same.
I'm not an expert in the actual implementation so I'd suggest you search through the best practice documentation and related info from service.sap.com
As I said though, it is very important to assess your needs as the Internet Sales solution is relatively complicated - if yuo just want the ability for customers to search for products and create orders then it would be much easier to create a few custom applications, say in an Enterprise Portal or just stand alone Web Dynpro / BSP / JSP / whatever... If yuo want the full catalogue type functionality then Internet Sales is the way to go.
For an idea of what can be achieved have a google for the Sony Style website - this is an SAP ISA (Internet Sales) solution running B2C.
Web shop out of box pretty much has all the functionality.
A few additions like user reviews, ratings, and amazon styled catalog menu can be added quite easily working with the classes and JSPs.
Look and feel (css, js etc) should be easily possible.
I am trying to do the following for a B2C Project
1. Trying to get an unordered list for all nested catalog items, so i can convert them with js and css to a dynamic drop down menu
2. Adding new products link in the work area.
3. Where to get all the product and image GUIDs?
4, Adding user reviews and ratings to products.