Je me répond à moi même car j’ai trouvé la solution à mon problème et si ca peux en aider certains 
L’idée est toujours d’utiliser les custom:button-card et d’insérer dans les custom_fields une carte picture-glance :
Voilà mon YAML :
card_pool:
styles:
card:
- padding: "0px"
grid:
- grid-template-areas: "'cam overlay' 'measures measures'"
- grid-template-columns: "1fr 0"
- grid-template-rows: "180px min-content"
custom_fields:
overlay:
- height: 180px
- background: linear-gradient(180deg, rgba(var(--rgb-card-background-color),0) 45%, rgba(var(--rgb-card-background-color),1) 100%)
- opacity: 1
- padding: 0
custom_fields:
cam:
card:
type: picture-glance
camera_image: camera.poolcamera
entities: []
card_mod:
style:
hui-image:
$: |
div img {
height: 180px;
object-fit: cover;
object-position: center -25px;
}
.: |
hui-image {
height: 100%;
}
.: |
ha-card {
border-bottom-left-radius: 0px;
border-bottom-right-radius: 0px;
box-shadow: none;
}
ha-card .box {
display: none;
}
overlay: <div></div>
measures:
card:
type: custom:button-card
name: Indicateurs de l'eau
label: "[[[ return states['sensor.pool_analysed_at'].state; ]]]"
show_name: true
show_label: true
styles:
card:
- padding: 4%
- border-radius: 0px
- box-shadow: "none"
grid:
- grid-template-areas: "'n tmp . ph . redox . sel' 'l tmp . ph . redox . sel'"
- grid-template-columns: "1fr 45px 5px 45px 5px 45px 5px 45px"
- grid-template-rows: "min-content min-content"
name:
- font-weight: "bold"
- font-size: "14px"
- place-self: end left
label:
- font-size: "10px"
- place-self: start
- filter: "opacity(40%)"
custom_fields:
tmp:
card:
type: custom:button-card
template: button_pool_measure
name: Temp
label: 23.5°C
variables:
color: "blue"
ph:
card:
type: custom:button-card
template: button_pool_measure
name: pH
label: 7.2
variables:
color: "green"
redox:
card:
type: custom:button-card
template: button_pool_measure
name: RedOx
label: 650mV
variables:
color: "yellow"
sel:
card:
type: custom:button-card
template: button_pool_measure
name: Sel
label: 3.3g/l
variables:
color: "red"
button_pool_measure:
variables:
color: "blue"
show_name: true
show_label: true
aspect_ratio: 1/1
styles:
card:
- padding: "0px"
- box-shadow: none
- background-color: var(--primary-background-color)
- background-image: >
[[[
let theme = hass.themes.themes[hass.themes.theme].modes[(hass.themes.darkMode ? "dark" : "light")];
let color_bckg = theme[`google-${variables.color}`].replace('#', '%23');
let opacity = theme['opacity-bg'];
return "url(\"data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http://www.w3.org/1999/xlink' viewBox='0 0 1440 1440'><path fill='"+color_bckg+"' fill-opacity='"+opacity+"' d='m 0,566 48,26.7 C 96,619 192,673 288,699.3 384,726 480,726 576,710 c 96,-16 192,-48 288,-42.7 96,5.7 192,47.7 288,58.7 96,11 192,-11 240,-21.3 l 48,-10.7 v 754 H 1392 1152 864 576 288 48 0 Z'></path></svg>\")";
]]]
- background-size: 100%
grid:
- grid-template-areas: "'n' 'l'"
- grid-template-columns: "1fr"
- grid-template-rows: "auto auto"
name:
- font-size: "10px"
- place-self: center
label:
- font-size: "10px"
- place-self: center
- font-weight: "bold"
- color: >
[[[
if (hass.themes.darkMode){
return "#FFFFFF";
} else {
return `rgba(var(--color-${variables.color}), 1)`;
}
]]]