Today I had a fit of inspiration and created a new blog design:

It’s currently named ‘rainbow sand’, which is a pretty terrible name — unfortunately my word-choosing ability was not similarly inspired. The result doesn’t quite mirror my mockup, due to uncertainty about how to best implement the offset fills. I may experiment with it further; we’ll see.
At time of writing, it’s WordPress-only, but I’ll be converting it for Tumblr. The slowest part is always the stylesheet, and that only needs to be done once.
Update: The Tumblr variant of the theme is now complete.