Sure
Using Blue Iris, set up a webcam to broadcast using your desired settings.
Go to Camera properties->Video->Text and Graphic Overlays->Edit
Click 'Add image...'
Browse to C:\Cumulus\web\images (or wherever your web images are placed by Cumulus) and select the image you want to use.
Tick 'Use transparent color key' and click 'Set color...' The mid-grey background of the image graphic should be on the bottom row of the palette 3rd from the right.
You can also adjust the transparency of the graphic.
Click OK and resize / position the graphic.
The graphic will be overlayed on the video and will update whenever Cumulus is set to update to the web. There has been a couple of times I have noticed that the graphic just disappeared, not sure why. Going back into overlays and clicking OK brings it back. I'm also using the 'Manycam' virtual driver so I can use the webcam with several applications, perhaps it is causing a glitch.
It is a pity that Blue Iris doesn't seem to allow dynamic text, but perhaps there is a way to interface between Cumulus using a 'text to graphics' program? It would also be great if sensor data like temp, humidity, pressure, etc. could also be shown using a 'dial' graphic.. not sure if this can already be done or if Steve has any plans to do this?