Web Application Styling / Theming + consistent icon set of about 80 icons

I currently have a desktop application that is being redeveloped for a browser environment. It is not a trivial application but a sophisticated data-heavy (grids / lists) application that requires a lot of information to be presented to the user.
I want a consistent style / theme which is modern, clean and simple and is a pleasant experience for the user who is often navigating a lot of complex and related data.

This is NOT traditional website design - we have an established interface layout / design that predominantly just needs the right colours applied in the right places to make it as beautiful and easy to read as possible.

A set of about 80 icons are also required - many are standard types of icons (new / edit / delete / save etc) but there are some specialised icons required to represent things such as "show items in final state", "create link to a new item", "version history", "relationship explorer"

The application's current layout / screens / windows are documented in the attachment as well as the list of required icons
I anticipate there would be some need to discuss and ratify precise requirements - probably giving the selected person access to the demo application so that they can use it and best understand the user experience.

I would like to understand what you have done before that is similar with any examples of both styling and icons.