Post certificate claim editing

I just claimed my certificate for responsive web design. I’m still new, so I’m wondering if I can still edit the projects I completed and submitted as I learn. I know there can be some more things that I can learn to clean up and improve the codes.
For instance, I would like to change the background to my Tribute page. Would I be allowed to do it?

as long as the link you submitted still pass tests, you can

if you want to do greater changes you can create a new version of the project