Board Thread:Support Requests - Designing Your Wikia/@comment-26257174-20151211133528/@comment-25508186-20151211135121

You can use css.

To change the size of all emoticons, use: To change the size of specific emoticons, use: ^ This would change the size of the ":)" emoticon.

Any of the above would go to your wiki's MediaWiki:Chat.css.