Need to have different texture on inside of mesh. What do I do?

For a reason I still haven’t figured out yet, I decided to make clothes and weapons from RWBY using Blender for a Skyrim mod.

Anywho, this jacket has different textures on the inside from the outside. This one.

And the inside of the jacket is textured a deep rich scarlet.

The problem is that it needs to have a different texture than the outside. What can I do? I’ve tried duplicating the entire object and flipping normals, but all that does is screw up the normals.

Not sure if it can be done with Blender Internal, but with Cycles you can use the ‘Backfacing’ input parameter to use two different textures for each side of the faces of an object.

BI can do the same:

Okay. Uh, for the game I’m making it for, I have to export it as a NIF file, will the Backfacing still hold over?

No idea. Maybe it needs Double Sided option on Object Data tab. Solidify modifier would make ‘real’ thickness. You need to experiment or get some info what your game expects for double sided stuff.