It appears that Gmail doesn't like the format of image names having a space in them. If you edit the image name to have no spaces this should resolve the issue. 

As an example, is you have an image called "this is an image.jpg"

Gmail will keep those spaces when it tries to load it, but the way HTML and links work, means that this will break.

So how you go about fixing this is simple! Rename the image before loading it into the system so that the image name is "thisisanimage.jpg", this will mean Gmail won't then try and re-code it and break your great looking email!