In the API documentation for Openweathermap, one of the parameters that can be called is the icon URL, which allows for you to use a plugin like Dynamic Image Portal to call the openweathermap image url (http://openweathermap.org/img/wn/[email protected]) where XXX represents the icon code called in the weather lookup of the current or forecasted weather.
![http://openweathermap.org/img/wn/[email protected]](http://openweathermap.org/img/wn/XXX@2x.png){kind=link}
Unfortunately HA’s implementation doesn’t call the weather icon, but since it is available I would hope it would be an easy fix to add a parameter to the calls.