eusing a piece of graphics is a useful technique, but there is more to the issue of inscribing graphics into a design composition.  Let's have one more look at the Oracom brochure.  We see that on the two internal pages, the strips of the dish-and-computer image have crisp linear edges, while on the last page, a fragment of the same image has an irregular shape and blurred, hard to discern edges.

This is a handy illustration of the two principal ways of including a piece of art into a page.  The first type, which could be termed displaying, uses rectilinear edges that do not correlate with anything in the image itself (that is, it may well be cut across any of its elements), so the image is thereby "framed" as if it is exhibited on a wall.

Sometimes, the edge of the image is additionally stressed by aligning it with other linear elements, or by adding a frame or a drop shadow (again, uncorrelated with the content of the image but treating it as an opaque rectangle).  Very rarely, another simple shape, such as a circle, is used instead of a rectangle to insert the image into.  Despite its pronounced edges, a "displayed" image can be partially overlapped by text and other elements (as are the artwork fragments in the Oracom brochure).

Displaying should be used for relatively complex graphics without a conclusive composition center, with numerous figures scattered more or less evenly on the plane.  It is easy to understand that no fancy cropping shape would work with such images; their content has no inherent spatial limit (you can always annex a piece of canvas and continue the composition, e.g. by adding a new figure or by extending the lines of the drawing), so it becomes necessary to set up a strict and uncompromising artificial boundary for the painting.  That's why, for example, the artwork composition on the America's Job Bank page could not have used any shape but a rectangle.