I can point you in the right direction..
go to Edit Templates then header
Find this
PHP Code:
<!-- begin navigation buttons table -->
Anything after that and before this
PHP Code:
<!-- End navigation buttons table -->
Is apart of those Navigation Buttons.
All i did, was take one currently codes and copy/paste. Then edit the path for the image and url for the page on my site.
To get those images to show up on your Portal I assume CMPS 2.0, I do not know if its the same for anything higher. You will need to do this.
AdminCP/CMPS settings/ Default settings.
And you will need to do this for all the images in this style to show up properly.
Type in bi2 into the boxes next to Header Replacements, Navbar replacements and Footer replacements.
I am sure hoof can elaborate and fill in anything I am missing here.