You can change things up on a twelve-bar blues by replacing the standard V-IV-I turnaround with a II-V-I turnaround. Ordinarily, you’d play bars 9-12 of a blues in E like this:
A II-V-I turnaround – this version, at least – could replace the A7 in bar 10 of the form with two beats of F#7 and two beats of B7, like this:
If you want to geek out on the theory, this works because we’re basically saying, first, “hey, instead of going from B7 to A7 to E, let’s just play two bars of B7,” which was a pretty common way to play the blues progression in the swing era. Next, the logic goes, “Well, if we’re playing B7 for two bars, why don’t we temporarily borrow the V of B7 – that’d be F#7 – to put some extra emphasis on the last couple of beats of B7?” That, as the classical cats like to say, would make F#7 the secondary dominant of B7 and would give you a rousing “V of V of I” progression – F#7 to B7 to E7 – to bring you back to E in a big way.
But if you have no desire whatsoever to geek out on the theory, here’s some tab, notation and audio to show you how it’s done. Have fun!
