OK i think you are totally confused so let me clear things up.
When i had the add-on from themes corp before y'all moved to your own company, the background image for page nodes and profile pages were fixed into one position.
This week is the first time i am re-installing the add-ons from your website because i needed the updated versions.
Now my suggestion to make the backgrounds fluid in your 2 add-ons came from my previous knowledge of how the themes corp version of the 2 add-ons worked. Now the backgrounds might just be fluid but i actually do not know this because i can not get the 2 add-ons to work.
So let me show you what i mean,

I have an background image set, but it will not show for the Page node background add-on
As for the Profile background image the background is set, but not showing on the profile page. Their is only profile cover permissions and i have it set right.
So in conclusion, i need help with getting both add-ons to work correctly,( by show the background image ).
Also wanted to know if the images are fluid or if they can be made into fluid images.
This website gives a ton of looks at themes that have fluid background images.
https://www.audentio.com/shop/XenForo-themes