
If you're looking at this image with an older browser, it looks like a static image. A ball sitting on the ground. With the latest version of Firefox, for example, it's bouncing like an animated GIF. And animated PNGs allow for a greater use of color (GIFS only allow 256, PNGs can go up to 24-bit), with partial transparency (the effect of the ball's reflection fading out like there's a mask layer there).
Hang on: this is a test of your browser...

I know the advertising boards are PNGs, and we're stacking the frames to create the semblance of animation. But at the moment, that limits us to four frames. If Oolite allowed us to have animated PNGs, we could have as many frames as we created, and have partial transparency (so a display could look like a hologram with the structures visible behind it).
And animated PNGs could be used for other effects. Animated wormholes, like in Babylon 5, come to mind. A repeating swirly pattern, just six or seven frames of animation, looped with 50% transparency. Or shields that were just a polygon that glowed when struck by a laser blast. Or shields for the stations. Or displays in the docking holes. Or arrows pointing to the docking holes...
The only problem, of course, is the lack of support for the format. You can download an APNG Editor that works in Firefox, but you have to render the frames one at a time. I couldn't find a GIF to APNG converter out there, and programs like ImageReady or GIMP don't (I think) support it yet. But once they do, imagine the interaction. Imagine something like this playing on a display screen, looped, rotating as the station rotated.

More examples of APNG here.
Thoughts?