I just used Firefox+Firebug to find the image URL of google street map. (open map.google.com, open firebug, click "inspect element", the click a map tile on screen).

The url near grand canyon, AZ is this:
http://mt1.google.com/vt/lyrs=m@146&...&z=7&s=Galileo

However the next tile of Las vegas, NV is:
http://mt0.google.com/vt/lyrs=m@146&...=50&z=7&s=Gali

Note the difference in mt0/1 and "s=" param. The URL of every tiles seem to be very dynamic now. Also if I change the z value to anything other than 7, it shows a blank image.

I tried many patterns in repository URL but none of them worked. Some resulted in "failed to download x maps". Some resulted in blank blue tiles. Does anyone have a working Google URL since 2011?