After getting a nice yellow silcone magsafe case for my iPhone, I decided to lean into the "duck" theme I stumbled on a few weeks ago:
The pixel duck was "inspired" by a google search for "pixel ducks", I then used browser-based tool piskel to roughly copy it (but using fewer colors.)
In making the actual background image, I was fumbling both with Acorn and Pixelmator... in both cases I ran into problems - either resizing without resampling, or just other basic functions. So I switched to a p5.js program. The "scale" trick to flip the image was a little wonky, and it took some finesse, but in general I like the control by doing design in code.
(Before this the theme was bumblebees, with an intermediate diver/blooper theme after I drowned buzzbuzz and had to get a new iPhone.)