Icon On mouse over window

Hi

I made a graph in a Grafana panel to see the PV yield.

In the PostgreSQL DB while I grab the PV values I also write weather info and the relative icon. Icons have the name of three char string:
10d
stands for the icon at the URL
http://openweathermap.org/img/w/10d.png.

It would be neat to show the icon in the window that appears whit the values when you move the mouse over the graph.

I could eventually predownload the icons so I have all of them locally.

How can I do that?