This app was mentioned in 1 comment, with an average of 1.00 upvote
Short answer: For iOS, I've heard Mobile VR Station (https://itunes.apple.com/us/app/mobile-vr-station/id959820493?mt=8) is decent. I doesn't do direct sync from web galleries like imgur or flickr, but has a whole bunch of fun stuff and a good user experience.
Long answer: I've been interested in the experience that you describe myself, so I built three viewers that do web galleries and phone galleries.
I was interested in Flickr photos, so https://play.google.com/store/apps/details?id=org.cmdr2.artroom gets photos from Flickr and displays in a spherical virtual room around you for casual browsing. Making this work for imgur or specific users doesn't look that tricky, and it should be straightforward to let people specify their own URL playlists, rather than use my predefined Flickr URL playlist.
There's an experimental mode in https://play.google.com/store/apps/details?id=org.cmdr2.places that lets you watch 3d photos from Flickr. Again, imgur isn't all that complicated.
Another redditor and I were interested in viewing photos from the phone in a more comfortable manner in VR, so I built https://play.google.com/store/apps/details?id=org.cmdr2.photos that lets you scroll through your gallery in VR by looking around, and view your photos in a large canvas (perceived 5 feet).
Since I'm an Android user and built this for myself, they're only on Android. While these may be famous last words - I wrote it in Unity which compiles to iOS too, and apart from some basic JNI hackery, I didn't do much Android-specific. So it could work in iOS with some nudging. I don't have an iOS device, but I don't mind open sourcing the code (#2 is already open source) if someone wants to take a stab at it.
If all of these look like crap, then I'm probably a fringe user and would benefit from feedback. :-)