Hi,
I would like to buy a digital picture frame as a Christmas present, which I could fill with pictures remotely (using owncloud). However, I am not aware of suitable frames which would support webdav, for example. Most cloud-based digital picture frames offer either their own hosting or rely on established services like DropBox.
Do you have any hardware recommendations or workaround ideas?
Nexus 7
cheapest and flexible screen you can get.
Including no-battery-mod also cheap to operate
But then you would have the cable dangling at the side and from an aesthetic viewpoint, tablets are usually not as nice as a dedicated digital picture frame.
Even though one could use a stand with a tablet, which is visually more appealing, I would still prefer having a true frame.
http://www.photovu.com/index.php
seems to work with WebDAV. I guess there are others. Would recommend to check with the vendors or open feature requests there.
This one looks super nice, thanks! Only problems: It's very expensive and out of stock.
Regarding your second recommendation: I've spend quite some time reading user manuals of different digital frames, which is rather frustrating, and at some point decided to ask here, as I imagined that others might have had the same requirements before.
Yes, only one I found 
But: maybe this works: http://airstash.com/wireless-storage.html
If I read it right, you can access any WebDAV Server and it just goes into the USB port of the digital frame you want to have ... if it works or not up to you ... feedback certainly welcome and thanks for promoting WebDAV as standard!
Wow, that's really neat! 
I have never heard about airstash, but if it works like it sounds it would, it could turn every digital picture frame into a webdav device. I think I will try it and give some feedback within the next weeks.
I think my enthusiasm was a little premature. Apparently, these sticks always open their own wifi network and also function as a webdav server within this network. So it wouldn't be able to connect to owncloud ;-(
See: http://www.maxell.com/Airstash/images/A02%20User%20Manual%201v1%20Final.pdf
If its a WebDAV Server you can "mount" it from ownCloud. External Storage Webdav connection might work and then you have it as a folder and can put stuff on it. But would need to be tried out ...
This might be an option, as the newer devices are also capable of connecting to an existing wifi network [1]. I will give it a try and see how easy / difficult it is.
[1] http://downloads.sandisk.com/downloads/um/connectv2-um-ios.pdf
I removed tha battery as my wall tablets are mounted flat and so the cable goes out at the back - no USB
And the nice thing with the nexus: no stupid home buttons or so at the front. Completely clean
Take one from ebay with a broken battery (you dont need it; just 5 min of soldering) and you get a perfectly flexible wlan touch display for 30€
I measured mine for aprox 4€ in electricity /year running 24/7
Is there really something cheaper?
That's a pretty nice idea actually!
In the end I will probably go for a tablet based solution and save myself the trouble of getting the wifi usb-stick to work. Alternatively, if I'll find the time, I might turn an old screen into a digital frame using a raspberry pi (there are plenty of tutorials online).
If you're into that kind of thing, this sounds like a fun electronics / raspberry pi zero project.