When it comes to building codes it is always best to follow them. There is a reason to address wire termination properly. Your family safety.
A blank decorative cover will leave a slight bulge with darts in the back drop material.
In basements you frequently can readily trace wall wire to a source. Once you think you have isolated the entire wire check it with a continuity tester. Sometimes if you are lucky DIY wire jobs can be pulled out of sloppy installs. In any event. For safety cap all ends in a box with a j-box flat metal cover, not a decorative plastic cover. If using a paper backdrop, cut out the portion that runs over the flat metal cover . Spackle up to but not over the cover and screws, then take the backdrop sample to a good paint match reader (HD, Lowes) and get a $3.oo sample made for painting the flat J box cover and screws. The finished job will be so secondary to your layout that it will not be a distraction.
Safe, done, legal, no fire insurance company pushback, no suit from next home owners.
Go on to next project.
