Screensaver
 

I've had my Forma for a few weeks and have been enjoying it. I came over from a Kindle Oasis. I like having the two navigation buttons of the Oasis, but the additional size of the Forma makes reading much more of a pleasure. Using the developer options to invert the screen for reading in bed with the spouse works great. I only need about 3% on the light to read. I use calibre to manage my books and have side loaded all content after I converted the books to kepub format (except for my Calvin & Hobbes).

I also enjoy using my own images for the screensaver option. At first I wasn't sure what images to use due to the somewhat odd dimensions of the screen. I've settled on the following images which display well and make me smile:

(1) book covers of classic books from my misspent youth. Doing a Google image search and using Tineye has allowed me to come up with nice quality images. Weathered, dog-eared paperback covers look great in e-ink.

(2) movie posters - the dimensions seem perfect for the screen. I am a fan of 80s movies and images of these posters are easily found.

(3) 1930s era WPA posters for the National Parks. I am a huge National Parks nerd and spend most of my summer in the parks (where I do the majority of my ebook reading). The posters look great on the screen. Tip of the brown round to Ranger Doug for bringing these posters back.

(4) I am also trying out a few album covers from back in the day. The dimensions are square, but still look pretty good on the screen.

What are other people using for a screensaver image?

The actual ebook cover! The one being read on the Kobo Libra.
On my Sony PRS350 I have various covers separately downloaded and it cycles through them.

Photos with various plants and animals, cropped to the exact size of the screen.

I'll have photos of places that I've taken rotating on my laptops and netbooks, where they're actually in color and crisp focus and can be enjoyed.

But for my ereader, I only want to see the cover of the current book I'm reading.

About half of my images are various M. C. Esher images, the rest tend to be random images either from photos I've taken or found on the Internet that I liked and that would covert to 4-bit greyscale and still look decent.

Given that my ereaders tend to live in sleep covers, I don't see the images all that often.

Cool idea about the Escher images!

I don't bother setting images to show on my reader because like you, I have a sleep cover so the sleep screen isn't on display.

When I was using my first Sony reader that didn't have a sleep cover I loaded a few personal photos on it. Of course not all photos look good in black & white so you have to choose carefully.

I use the default screensavers on my Kindle and Kobo e-readers, which are the deck of writing-related images and the cover of the last read book. I think I'm just using the default screensavers because I want to stick to the stock software that comes with those devices as I use them as part of some research I'm doing privately.
However, on my Likebook e-readers, I have one giant deck of screensaver images. As of this reply, it stands at 129 images, which include:

1. Most of the images from the defunct linux.pictures website (it was still around when I first got my Mimas), which are still archived online by GitHub user 'nixcraft' and others. I used a script they provided in order to scale the images, and I manually scaled the rest using GIMP and a template I've yet to release.
2. Screenshots of comic pages I like, that I capture while reading them, including from 'Sarah's Scribbles', 'The Fuzzy Princess', 'Magnificatz', and 'Isle of Elsi', to name a few.
3. Digital copies of prints given away through comic Kickstarter campaigns I backed, including some from Nick Prolix and Sarah Graley
4. The iFixit Repair Manifesto
5. School library posters from authors/illustrators Jarrett Lerner and Sarah McIntyre (I like their art styles), via their website and blog respectively.
6. A collection uploaded by this Reddit user.

I mostly use night mode (inverted video) and that increases the ghosting on my Clara HD a bit. For that reason, I have my Kobo to show no screen saver image, so that when I open me sleep cover my screen is clean with no ghosting.

I use the cover of the book I am reading.

I just rendered some fractals in B&W for this purpose! I'll have to experiment since they're a bit dark on an unlit eInk screen. What looks great on my LCD iPad isn't as impressive on a gray unlit substrate.