Instead of playing the standard two string shuffle riff or variations in the same style, it often sounds effective to use the rhythm guitar like a horn section. This often means using short punchy rhythms and whole or partial chords. Many rhythms used by horn sections can be transferred directly to the guitar.
One of the most common rhythms used is known as the Charleston rhythm, (named after the dance, but came from Africa originally.) Here is the basic rhythm applied to 9th chords.
It is possible to move this rhythm to several other positions within a bar. In this exercise it is moved forward by one eighth note. Notice the different effect this creates. Experiment with other placements of the charleston rhythm within a bar.
Now try putting the previous two rhythms together to form a two bar pattern.
This two bar pattern sounds great when applied to a 12 Bar Blues progression.