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For pictures (local and social media feeds) I use dayframe. It can play them locally on your device in the app, as Android Daydream screensaver or on a Chromecast.
I used an app called Dayframe, which is pretty easy to link to a Dropbox folder. You can also set it to turn the screen on and off, so you can set the hours it comes on (the one I made comes on around 5 and turns off around 10).
No special trick to charging, they just leave it plugged in all time. It's been like that for a year with no problems.
I'm a fan of personalized information displays just hanging around. I used to have several Chumbys and I really miss them. I still haven't found anything comparable. Smart mirrors are kinda cool, and they get closer to that concept. There are a few android smart mirror apps.
I settled on using them for home automation status and control. I'm up to 3 tablets so far. Check out my video wall mounted tablet for OpenHAB
If you get SmartThings, action tiles looks really promising.
Could make it a picture frame while you're not actively using it
You've already mentioned the remote.
You could turn it into a dedicated media player
You could turn it into a permanent or when needed wireless security camera. I did this with an old phone of mine, and had a server set up to store photos when motion was detected during a certain time, etc., etc. You could also have it email stills when motion is detected.
A digital photo frame
Offline GPS device
I use an app called dayframe on my tab 10.1 docked.
I use Dayframe [link] but there are other apps available. Google photos for example.
Something like this [link] with a search running for birthday on 500px and instagram.
I did this a while back using the Dayframe app. It worked really well.