Here is an example of a post with before and after explanations ... and pictures. Here is put the text of how the job went/what you did etc etc.
See how awesome it looks .... (put a description of work etc)
Here is the finished work. blah blah blah
This is just a mock up of how a Before/After Blog entry will look.
Might be a good idea to get some nice referral letters from some of these jobs that say how happy they are with you and the work done.
