I am now writing my PhD dissertation and the book style is almost ready. I am looking to get some professional advice on how the actual book looks like. Not sure where to post the sample pages. Is the main site the right place for these kind of things?
The main site is for question and answers which are of interest for the public.
For getting professional advice regarding your individual design, have a look at this list of professional TeX consultants
If I understand you correctly, what you are searching is a skilled book designer/typographer. How to design your book (thesis) depends on your local typographical traditions, the content of your book, your audience etc. The goal is to communicate in an effective way. You may start with Robert Bringhurst’s excellent book, The Element of Typographic Style.
Bringhurst ideas are amalgamated with
tex into the ClassicThesis-package. In this package you find lots of good designing ideas and code for typesetting your book.
When you have decided your layout, then you can ask the forum both how it looks like and coding tips. But remember that taste is personal; what you think is nice, I may find horrible (I support the Bringhurst style).
Tips on how to word your questions, avoiding to have them closed as ‘to localised’, you may find in this thread: Is it OK to ask for suggestions concerning a table layout?
Maybe one of the best places for expert opinions on such matters is http://typophile.com/