Hi Lobna,
There are two aspects of personalizing tbh. The simpler and more straight forward is the user interface; theme colors, placement of controls, etc. This can give a site a completely different look and feel, but doesn't change the functionality.
Changing the functionality enables you to customize the modules to do what you want them to; this enables you to have completely unique modules for your site. I've found that the Articles module, from data tables, through DAL and BLL are great to use for this customization. On my site
Computer Scribe I modified the Articles module to build a Resources module to list on-line resources. The Portfolio module is another variant of the articles module.
I belong to a SQL Server user group and am in final testing of a web site for the group and I based it on the tbh n-tier model as well. The group has monthly meetings and a job postings section; I based both of these on the Articles module as well.
By creating specialized modules, all based on the architecture of tbh modules you can have a library of modules that you can mix and match to build multiple unique web sites, quickly and easily, as well as tailor to the specific needs of your client.
I hope this helps.
Steve