Reestablished Illinois Cover Photos

Today, I revamped the cover photos for Illinois's State Route and US Route pages.  Some were changed, some were improved, and some were left alone!

I added a couple more photos to fill in some holes on the I-55 and I-57 pages in Illinois.  I also added green terminology links to the Illinois Interstate pages for I-24, I-39, I-55, I-57, and I-64.