Keep image sizes fixed regardless of the site width (Harris template)

Hi guys,

I am trying to ensure than an image stays fixed at the same size regardless of the width of the website. I'm particularly trying to make sure the images do not scale when on mobile.

I would also like to try left align one image and centre align the other image within the block on the page. 

This is the code I have tried but have had no luck getting anything to work yet. I know I am referencing the correct images as I can give them background colours, but adjusting the size and positioning is escaping me.  Any ideas what I can try?

@media only screen and (max-width: 640px){ 
[alt="spacer-left.gif"] { 
  min-width:1400px  !important;
  height:5px !important;
  object-fit: none !important;
  overflow:hidden !important;
}

[alt="spacer-mid.gif"] { 
  min-width:1400px  !important;
  height:5px !important;
  object-fit: none !important;
  overflow:hidden !important;
}
}