By "framing device", I mean to add context to the picture so that it's obviously not real -- so that the monkey viewing the image perceives the monkey on the screen as a representative icon and not another live monkey.
One option is to literally put it in a picture frame, especially scaled down to much smaller than "life size". Make it a full screenshot with the start bar, have the app unmaximized with some desktop around the borders with "My Computer" peeking out, leave a mouse cursor on the image, show the mouse hovering over some modal rollover state like a menu.
The 3/4 view is fairly extreme -- skew it isometrically so that it's not on the normal plane. You can fall back on the shareware standby of photoshopping it onto the front of a glossy retail box with a UPC code and system requirements fine print on the side.
CoverFlow is kind of the nuclear option, one of the most extreme slideshow effects you can get away with, that combines all of the previous techniques: http://www.apple.com/safari/whats-new.html#coverflow -- frame the hell out of it on a contrasting 3D background with shadows and skewed reflections, and skew the
remaining images isometrically into a carousel of cards. Note that Apple's screenshot of the effect is scaled to 1/9th of real size, and itself has a reflected (though not skewed) shadow applied to it!
He's saying you should alter your screenshot to make it more obvious that it's not the real thing. Frame it with an image of a monitor, give it a drop-shadow, etc.
