I really love big pictures, especially panoramas.
These days, computer vision techniques like graph cuts, gradient-domain blending, and feature-based alignment make creating panoramas very easy. Even using low-end equipment you can create pretty cool images. On the viewing side of things, using image pyramids helps create really slick ways to view huge images.
To see what I mean, check out the panoramas of Israel and Jordan I created based on the photos I took on my recent trip to the Middle East.