Vigilance Theme and Header Image

I have been trying to get a header image to show up on my site (https://www.mingle-mangle.net) and have managed to make it so it works only on some browsers. I’m not sure what’s wrong, but the image itself shows up on google chrome but not on firefox or internet explorer. The header location is https://www.mingle-mangle.net/wp-content/themes/vigilance/images/minglemangle.jpg.

I’d love some help if anyone knows how to make it show up.

I also was hoping to get rid of the preexisting banner that is below the line. Though wasn’t sure how to go about that.

Any help on either issue would be greatly appreciated. Thanks.