I can't speak for IGFA rules other than you have to submit good quality photos and a leader sample along with your weigh certificate and witness information.
As far as putting a fish on your wall, you are already half way there. I would recommend a reproduction. I just received my 5 pound brookie that I caught this spring and it is extremely hard to tell that it is not a skin mount. All you need to supply is good pictures and measurements. The cost was also substantially less than a skin mount. A nice aspect is you can let the fish go and still have a high quality mount.
Whatever you do, don't wrap the fish in newspaper. Take an old towel, get it saturated with water, and wrap the fish. Put in the freezer and enjoy looking for a taxidermist. Hope you catch that 14 pound bonito.