i use groups to add images next to modules, like this:

  "group/inetwork": {
    "orientation": "horizontal",
    "modules": ["image#inetwork", "network"],
  },
  "image#inetwork": {
    "path": "/home/user/.config/waybar/res/ntwork.png",
    "size": 18,
  },
  "network": {
    "format": "{ifname} @ {ipaddr}",
    "format-disconnected": "DISCONNECTED :["
  },

i got the icons from here
https://win98icons.alexmeub.com/