Rafterlife is a cave flyer that I've been hacking on for a few weeks now. The setting is a procedurally generated miniature planet. Everything in the game is grid-based; including the player's ship (a.k.a. raft), which you can customize by adding or removing blocks.
Since regular grids have an annoyingly blocky look and feel, I'm generating the blocks as a Voronoi diagram seeded by a square jitter. See the blog post Jittered grid vs Poisson disc by Amit Patel for an interactive illustration. The seed points are constrained to the central 25% of each square (50% of the x-axis multiplied by 50% of the y-axis), so that each resulting polygon will have at most eight neighbors. The polygons can then be used directly in Box2D.