Use the `icon` slot to add system icons.

```html
<div class="flex gap-12">
  <sd-radio-group value="1">
    <sd-radio-button value="1">
      <sd-icon label="landscape" name="system/image" slot="icon"></sd-icon>
    </sd-radio-button>
    <sd-radio-button value="2">
      <sd-icon label="landscape" name="system/image" slot="icon"></sd-icon>
    </sd-radio-button>
    <sd-radio-button value="3">
      <sd-icon label="landscape" name="system/image" slot="icon"></sd-icon>
    </sd-radio-button>
  </sd-radio-group>
</div>
```