Watch the Blues Rhythm Voicings online guitar lesson by Larry Carlton from 335 Improv
Blues rhythm parts can be drop-dead boring unless you know how to bring them to life. Even while laying down big, fat chords, you can add interest with upper partials, like using 9 chords and 13 chords in place of standard dominant 7's. Notice on the video how a strong pulse is created by using left-hand mutes. With a staccato feel, the straight-8ths rhythm has some feel and forward momentum.
For smaller voicings, which can be especially useful for little comping stabs, drop some of the lower and upper voices played on the outside strings. Just be aware of which chord tones you lose when you drop notes. Usually it's a pretty safe bet to drop the root, since the bass player is likely covering it.
A good rhythm part builds over time. In the example played here, I start out simply and then get a little more elaborate with partial chords, half-step slides, leading tones, and rhythmic punctuations. These are all great tools to work into your own playing whether you're laying down a comp for a soloist or recording a rhythm bed for a tune.