Header Image

That’s strange, because 300×90 is the suggested size.
I tried to reproduce the error but it didn’t happen, sorry but it’s almost impossible to help without see the page with the broken icon.

Okay, I have the broken image up.

Although I’m using the exact size suggested the image shown as broken is much larger.

https://www.twangnation.com

Sorry, but I can’t see any image.
In your source there’s this image address:
https://example.com/uploads/2013/09/cropped-capsmall.jpg
I believe it’s the one you say, but it isn’t visible.
Seems settled up in a local server.