When you use the incoming webhook, you register it with a channel and give it a name.

I didn't have an image available when I first set it up, so I went in reconfigured the connector and uploaded the "seq-logo-3 small.png" in this bug report.

Hit save.

But it doesn't take effect on new messages.

Going back in to configure it, it gets distorted as shown in "Image distorted after upload.png".

And all postings still show the default logo in "Image still default.png".

Seems image setting is broken.