Here's why:
* Palindromes read the same forwards and backwards. "Hang" isn't a palindrome.
* "Wall covering" is a phrase, not a single word.
To get closer to a palindrome, you could use the word "paper" (which is a type of wall covering) and the phrase "re-paper" (meaning to hang new wallpaper). While not a perfect palindrome, it gets close to the idea.