Actually, the difference between those curves is noticable: second team has a dashed outline that is reflected in a legend. Unfortunately, the number of distinct colours is limited, and the same colours are applied to the next group of teams in a league but with dashed outlines.
Why didn't the image work?
Because your URL does not contain valid image file extension, e.g. gif, jpg, png.
The following image:
http://www.newhavensoft.net/images/ow120_25.gif
does work ok:
