Watch the Comping 2-Chord Pattern online guitar lesson by Larry Carlton from 335 Improv
You can find a world of options even within the simplest chord changes. All of the improvs in this section are based on the vamp from my tune "Rio Samba," which features a two-chord change between F9sus4 and F9. Then it just modulates down a half step to E9sus4 and E9.
When comping, you never have to be stuck strictly with the given changes for a rhythm part. Instead, look for opportunities to alter and expand the changes without straying too far from their basic tonalities. For example, an Eb triad can be used in place of the opening F9sus4 chord. And since the notes in an Eb triad match the upper voices of a Cm7 chord, you can substitute Cm7 every time you see F9sus4.
Check the PDF or PowerTab for notation and tab of the voicing options that I play on the video. Then explore inversions of your own, incorporating new bass and upper-string notes. As you'll see, it can be as interesting and exciting to improvise a rhythm part as it is to improvise a solo.