Steps to set custom svg icon:
Step 1: Go to your Grafana dashboard and make new dashboard.
Step 2: Now add canvas panel visualization
Step 3: Now Go to your grafana directory which is by default install in the path given below
C:\Program Files\GrafanaLabs\grafana\public\img\icons
Step 4: Now go to the start menu and search services
Step 5: Now search for grafana running service and restart it
Step 6: Now open your dashboard and click on add item
Step 7: Now select the custom svg which you have created
Final Outcome: -