Network design for switching

Since i come into networking field. I just learn the how to suggest proposed design to customer and how to give  real solutions to customers in order to fix with customer budget, project quality and some kind of redundancy. This section i wanna introduce for switching design. Based on below diagrams.
Normally network engineer create vlan group based on customer department and some based on location and some based on customer proposed subnet information. From my diagram i just create vlan based on department like Manufacturing , Marketing , Sales ...etc. I design switching into 3 tier network. Accounting , Engineering, Sale and Human resources department are connecting to 1st tier switch.  Manufacturing , Marketing, Executive and IT department are connecting to 2nd tier switch. All these 1st and 2nd tier switches connect back to 3rd tier CORE switch.

Here comes with Connection link for my design as well. 1st Tier switch to 2nd tier switch will be trunk link if they belong to more than one vlan.

The final picture is considered the case for network redundancy. In this design , one of Core Switch have problems or down, the other core switch can handle to get network connections.

Okay. That's for  some network drawing. Hope reader on my blog is happy to see and get idea on it. :)