Everything gets broken into smaller chunks, and those chunks get put into small columns. The pictures are small because a big picture will throw things off.
I'm not sure, but I think Japanese people (and Asians in general) have very different rules for negative space - they either don't use it at all (and pack the design like blocks of tofu) or will use it in a very intentional way. It's rarer (as far as I can tell) for negative space to just relaxing filler, it's more a bold statement similar to an attention-grabbing graphic.