I'm also interested in this. I hate the way it names pictures. It makes things difficult when you sort by filename in a directory listing.
I've changed the date format under Settings > Date & time > Select date format > to MMMM/DD/YY but it has zero effect on the way the camera names files.
So frustrating. Samsungs camera does filenames about perfectly. example: 20140827_135746
They even add down to the second on the name. LG just adds a letter if it's a picture taken within the same minute.
edit: Dang. Even looking clear back to my original Droid1 they had this correct. Filenames were "2010-01-29 21.26.14.jpg". How could LG mess this up so bad?