Windows Application like Matured Application

Hi,Thanks Advance

I have build One Windows application..for this application i am maintaining Two Project. 1.MainProject(Forms) 2.code project(DLL).Why i am doing like in future may i can use Web application also.

In code project maintain entity layer and also DataAccessLayer. I call this Codeproject dll from Main Project. 

Now  I feel i want to add extra future like structure and matured application.  my Query is i want to add future like 1. Log Maintain 2. ProgramError Handling maintain separate page..i don't know what i will include extra future. but i need all futures to this application.Please give solution, and idea, code etc...please ASAP.