according to some, visual rhythm can be described in a variety of ways, depending on what's happening with visual patterns, as well as with the flow of how the viewer's eye is drawn across an image. the artlex dictionary defines "visual" rhythm as "movement by the repetition of objects".
here's an example. this photograph is of a white picket fence somewhere here in austin, and was taken on a sunny afternoon.
i pulled this photo from my collection in an attempt to illustrate the idea of "progressive rhythm"--which basically means that the shape & size of the pickets in the fence appear to decrease from the left edge of the photo to the right edge. See another definition at acrstudio.com
the alternating light & dark areas of the photo also indicate a rhythm type of visual rhythm.
this next shot of the fence was taken with another "perspective" in mind.
another visual design course (this one @ cornell) defines linear rhythm as the "characteristic flow of the individual line"
ok...so why talk about visual rhythm?
because visual rhythm is akin to musical rhythm
...musical rhythm is akin to physical movement
...and we can observe physical movement through visual rhythm.