Today’s second glitch:
Because heads is plural, the missing apostrophe belongs after the s in ancestors’. (More than one head means more than one ancestor to have owned the heads, unless this family was really weird.)
Change look up on to look up at.
Because heads is plural, change appears to appear.
Did you catch the typo in the last line?
You enter your new neighbor’s home for the first time, look up at the wall, and see what appear to be his ancestors heads’ on wooden wall mounts.