Markdown img background - card-mod?

How can I integrate the background without losing the ha-card style?

type: markdown
content: >
  <center><img width='50'
  src="https://www.freeiconspng.com/thumbs/logo-whatsapp-png/logo-whatsapp-png-free-vector-download-7.png"/></center>
card_mod:
      style: |
        ha-card { --ha-card-header-font-size: 20px;
        border-radius: 10px 10px 10px 10px;
        border-width: 1px; border-color: green; }
        ha-markdown:
          $: |
            img { 
              background-color:black;
            }        
            

go to the main card-mod thread → 1st post → link at the bottom titled “fantastic post” → others → combining “.:” & “$:”

solved:

type: markdown
content: >
  <center><img width='50'
  src="https://www.freeiconspng.com/thumbs/logo-whatsapp-png/logo-whatsapp-png-free-vector-download-7.png"/></center>

card_mod:
      style: 
        ha-markdown:
          $: |
            img { 
              background-color:black;
            }
        .: |
         ha-card { --ha-card-header-font-size: 20px;
         border-radius: 10px 10px 10px 10px;
         border-width: 1px; border-color: green; }