Image Full Width Size

Hi everyone,

Hope you are all well.

I am trying to create a banner/subject heading that I want to go at the top of each module. I'm having to design it to stay in line with my companies branding therefore, text over image etc is not ideal.

I've managed to create the image but every time I upload, a white bar appears to the left - this shows up in the preview of the course as well. 

How can I ensure the whole image width is blocked in and continuous? Does anyone know the dimensions/sizing of the image full width I can work with to create a banner.

I have attached a picture to show you, however, I can't show you the whole picture due to the nature of the project.

Thanks