Okay, I just tried on 2 jellybean devices. Hold down your finger on the pic until the blue bar appears up top. If there is no trash can icon press the vertical 3 dots upper right corner. From drop list press delete.
If it still doesn't work, factory reset. Or if rooted clear dalvik cache. (All the apps are optimized to run on your hardware and put there as Dex files)
2nd option, use a file explorer to delete them.
If the pics are synced from g+ or picassa you'll need to delete them from those apps.
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