I'm probably in the category of teaching my Grandmother to suck eggs here but, I have just opened an account in karafun.com For just under £7 per month you can access thousands of songs to use as backing tracks. Not exactly meant for guitar players as such but, I have found many great old and new tunes that you can eliminate the vocals from and, play along. Playback quality is good, real instruments, not midi. If you already know all this,,,,,,,,,, sorry.
Kind Regards
Roger