Google's John Mueller was asked if swapping out your logo on your site for the site's birthday with a special birthday logo can hurt your SEO. John said on Twitter "I've never seen issues around that." In fact, Google does it all the time on its home page and heck, I swap out the theme on this site for special days as well....
-
Changing Your Logo Hurt Your SEO Or Google Rankings? Probably Not.
seroundtable.com