Ok So it's slightly different from flashing a phone like my galaxy S2 I9100.
On my phone I should flash a ROM and a .zip package of gapps (google apps) among which is the gallery app.
Since you don't have to flash such a package I wonder whether you came from a KK ROM.
You said you rooted it like this. So I assume you came from stock KK ROM which comes with your AT&T Note 3, which should be no fine. But you can check that though.
it could be a corrupt file somewhere on your device. You're gallery app will try to show it or make a thumbnail out of something which will result in a crash. For this you can try other gallery apps (I liked quickpic) and see if they crash.
Maybe you can unprotect the folder/files simply by:
thread it appeared to be an old SD card so that could be the problem as well.