Alternative to webcam for videoconference app?

My company has decided that its engineers would welcome losing an hour of productive time once a week in order to participate in a videoconference, specifically by using the Bluejeans Network app.

While giving me the speech about how great this was going to be, my boss let it slip that an unnammed engineer in another sector has figured out how to replace his camera feed with other images.

So... I could use some help from you wizards with how to do just that. Audio I have down cold (that's my job), but video throws me. Is there a simple Windows setting, redirect or hack that would tell a videoconference app such as Bluejeans (or Skype, etc) to display a static image file versus from the computer's webcam? Bluejeans has the ability to share a file, but I got the impression this was a hard redirect from the camera feed, such that it was never displayed.

I'm sure the other guys are not interested in watching me surf TigerDroppings while I listen to each of them repeat the same report each week ("spent most of my time out at the site adjusting on that old reframulator, it's gonna blow any time now"), just as I'm not interested in watching them yawn at my report.

Any ideas? Here's a picture of a cat on a Roomba for your troubles.