That’s a common method that Alan mentions, and it works.
B&W shots can be blown up larger than color ones and still look sharp, especially if you play with the gamma.
Another one I like is to create a tableux scene and put the graphics within the tableaux. Say, for example, the photos are of a firefighter. Make a tableaux of props of fire-fighting gear; boots, turnout coat, helmet, maybe a hose nozzle, stuff like that… Set up the shot, light it nice, and you can add a monitor in that scene that shows the shots, or you can project the shots across the scene, or make them look like a sequence of frames the camera pans across… whatever your imagination, time, and budget allow.
Multiple picture-in-picture effects can also be used, kind of a Mondrian look, where you blow up multiple, detailed but oddly-cropped sections of the still and layer these to make up a larger image.
You can also try to use creative cropping thru the use of objects as masks, as well as cutting up the photo in photoshop, breaking it into layers, addigng extra elements, and animating the layers.
You cna also try to increase the picture’s apparent size by using something like the Genuine Fractals plug-in.