I started thinking more about projects I wanted to do with my E-ink/ E-paper display and brain dumped some possible types of project choices.  I then did a search of E-paper projects on some of the project tech websites.
I did not find many different uses, they were all very similar so I thought it would be fun to place my list of possible projects and pros\cons here.
Some of these suggestions are suitable for larger screens, and some are more suitable for smaller screens or colour screens.

A door open or closed status, this could be a gate sensor or garage door sensor that displays the status inside your house, ever forgot to close that laneway garage door?
People who entered a house, room, place or moved an item. A fridge alarm that once triggered displays there was indeed an intruder. 
Keeping an inventory, this is OK as long as the inventory is not constantly changing.
Text, something like poetry or short passages, inspirational messages or pictures.

A common use for these displays is miniature weather stations or plant monitors.
Check the water level on plants or the weather forecast and choose whether to water the plants today or not.
Another option is basically items like name badges, graphs, pictures and static images. The main advantage is the low power with image retention.

Bad uses E-paper displays are games like side scrollers.
Most E-paper displays do not have a backlight so are less useful in low light conditions.
Clocks and stop watches that require lots of updates per second will probably reduce the life of your display. Same with the speedometer and tachometers. It looks like there are displays that look like they are made for clocks specifically.
Watching animated images is not going to be possible on low-end displays.

Another consideration is the processor used to drive the display.
A lot of ideas listed above include the use of updates via Wifi or Bluetooth. At this point a processor has to transmit and receive periodically. Transmitting periodically reduces the chance of using regular batteries because they won’t last very long unless there is some sort of low power / sleep.
The options turn to rechargeable batteries.  The more times that you transmit and receive equates to having to recharge more often. It occurs to me that plugging the device in to the wall and\or recharging the unit frequently, sort of defeats the point of the low power E-paper display. (At this point coolness is a consideration), but a different type display might be a better choice.