Choose any amount of columns with any post width, customise post margins and padding. Make some posts double or triple the width using tags or every X posts. Have posts shrink to fit page or limited to any content width.
Don't like headers? Ok, have the header display as a post, or a double-width post. Do like headers? Have it fixed to the top so you can always see it.
Display photosets the normal mosaic way with a custom image margin, as separate images, as only the first image, or as a slideshow that slides or fades, with arrows or dots or that changes automatically. Can be chosen blog-wide or curated on a post-by-post basis using special tags.