Here's a little Texas Blues Guitar Lick for you. Guitar in this example is tuned down a half step. You can download the backing track and play along. The backing tracks for this guitar lick is 25 - Eb Medium Texas Thang it is from www.freejamtracks.com - used with permission.
The lick and example improv following it are based around the E Minor Pentatonic Scale. If you find this lick too easy or boring the King of this style of playing is Stevie Ray Vaughan. A great place to start with the study of his playing is "Pride and Joy".