The first letter(s) of the site name is the default icon for beta sites. Only a few have a different icon.

A question mark wouldn't work, it could be anything. When I see your (?) icon, I see “question mark”, not “parentheses”. And Puzzling is already ??.

There are several icons associated with Emacs. GNU heads are associated with GNU Emacs; this site is about all Emacs variants (even if pretty much all questions are about GNU Emacs, which is the only version with ongoing lively development, apart from derivatives thereof), so this won't do. Other icons associated with Emacs include the kitchen sink. A kitchen sink icon (without the word GNU inside, to avoid any implication that this site is associated with the GNU project) would be nice.

There may be a kitchen sink icon with a liberal license that Stack Exchange could reuse, I haven't investigated this aspect.

The first letter(s) of the site name is the default icon for beta sites. Only a few have a different icon.

A question mark wouldn't work, it could be anything. When I see your (?) icon, I see “question mark”, not “parentheses”. And Puzzling is already ??.

There are several icons associated with Emacs. GNU heads are associated with GNU Emacs; this site is about all Emacs variants (even if pretty much all questions are about GNU Emacs, which is the only version with ongoing lively development, apart from derivatives thereof), so this won't do. Other icons associated with Emacs include the kitchen sink. A kitchen sink icon (without the word GNU inside, to avoid any implication that this site is associated with the GNU project) would be nice.

There may be a kitchen sink icon with a liberal license that Stack Exchange could reuse, I haven't investigated this aspect.