Don't see the advantage of eInk for a digital photo frame. Presumably these stay in one spot and can be left plugged in? Would think that a bright LED display would give much better picture quality.
Personally I prefer using e-ink panels for my home DIY projects because I'm sensitive to light polution - I don't want half my home to constantly be glowing at me from every direction. E-ink panels are not emissive, so they don't have this problem.
I'm even pretty annoyed at spurious LEDs. I appreciate for example that Sonos speakers let you turn off their status LEDs. It just makes the ambiance calmer.
The exception is very interactive stuff like https://hackaday.io/project/190477-hyelicht where I used an LCD for the embedded touchscreen in the shelf, but powered down unless you touch it.
But you can put them in places in your home where it's not practical or aesthetic to run cabling to plug them in (e.g. fireplace mantel or hung up on a wall) and have a battery life that is measured in weeks or months rather than days.
You'd be right about the superior picture quality, though, but as the common use would be family photos that you see in passing to make you smile and may be quick snaps, the quality of e-ink is likely to be enough when it's a quick photo of your loved ones.
Some people do not like the idea of powering a device they are not actively using. If you are not watching the piece, a «bright LED display» seems like a waste of energy.
