These two posts were published in 2011(!) at Mike Cane’s xBlog:
Screensavers For eInk eBook Devices
Back then, eInk eBook readers mainly had screens of 600×800 resolution.
Today, the new Likebook Ares Note has a screen at 1404×1872.
So, I’m not saying those old posts will necessarily be useful (I didn’t check out what they link to — so beware of possible 404s) but perhaps they will give people some ideas to create their own.