You can use the FabricUI icons which are available here: https://developer.microsoft.com/en-us/fluentui#/styles/web/icons

Find the name of the icon you want (e.g. "sunny" or "rain"):
[![enter image description here][1]][1]

Then include an iconName attribute to specify the name e.g.

    "attributes": {
      "iconName": "sunny"
    }

Then use an IF statement. The following example assumes you have a column called "Weather":

    "elmType": "div",
    "attributes": {
      "iconName": "=if([$Weather] == 'Sunny', 'sunny', if([$Weather] == 'Rainy', 'rain', ''))"
    },

So if the column "Weather" contains a text value of "Sunny" then the **sunny** icon will be displayed. If "Weather" contains a text value of "Rainy" then the **rain** icon will be displayed.

  [1]: https://i.sstatic.net/UjWKP.png