There's "Look & Feel" for individual portlets. On
Content Pages, you can also create your own fragment that introduces
random CSS (the CSS can be scoped to the page, it's not automatically
limited to your fragment).
And you can also add it to you theme - either by redeploying the
theme, or by creating a ThemeContributor.
As other bugfixes might come in as well, potentially security
related, I'd recommend to not resist updating for too long though
(unless you're on DXP, then there's no reason not to install the
latest Fixpack).
