My slide layouts usually have a white frame around them, even big images I don not let "bleed" of the page. Why? My slide decks are usually a mix of these minimalist big image slides and more traditional, dense, consulting-type slides. The big pictures usually go in the front of the deck to sell the idea, but for financials, roadmaps, etc. I need a different format. Mixing two styles of presentations gives the deck an inconsistent look.
(The exception would be tracker pages, or section separators, which I usually stretch over a full page).
That "box" gives you some new design opportunities though; you can make things pop out by putting them outside the frame on purpose. This is technique that is often used on magazine covers. Below are some slides from the store where I used this technique (clicking them takes you to the store).
