Custom CSS is an extremely powerful way to customize the dashboard look-and-feel (it's like a theme, but without a theme manager). Once the current bug (Custom CSS in Dashboards) is fixed, it will be amazing. It would be even more powerful to add the tile template name to the dashboard tile
<div> class attribute. Like this:
<div class="tile dimmer" ... /> <div class="tile door-status" ... />
This would allow for easy template-specific tile customization using CSS. Thanks!