Voici de quoi t’amuser déjà (avec card-mod) :
type: entity
entity: sun.sun
style: |
ha-card{background-color: coral;height: 300px !important;}
.header{background-color: green;}
.header .name{background-color: gray; color: white; font-size: 10px;}
.header .icon{background-color: magenta; color: blue; transform: scale(2);}
.info{background-color: red;}
.info .value{background-color: orange;}
.info .measurement{background-color: yellow;}