I wanted to know if it's possible to do Windows 7 Deployment via a Linux PXE environment, or does the PXE server (TFTP, Images) have to be Windows Server 2008?
No it is not a requirement for Windows 7 to be PXE booted from a Windows 2008 server. Linux distributions can sometimes take time to "support" a new version, but in most cases all that needs to happen is that the bootloader files need to be added to the PXE server.
Here is an example.
The first Google search hit reveals that it is possible. And gives you a step-by-step guide to achieve that: