Custom theme development


I am trying to develop a custom theme for Plone 5 with python version 3
I am using a already available theme for plone 5 and using this theme as base and doing my customizations on top of it.
Link to the Theme GitHub - quintagroup/quintagroup.theme.sunrain: Free Diazo theme for Plone

When developing this theme I understand the pages are combination of plone framework's resources as well as Theme resources.
So I have few images on my home page which are coming from theme and they are getting displayed after a webpage which exist in Plone "Welcome page" I want this Welcome page to come after these images but I am having hard time moving things around in the theme.

Looking forward to some responses.