Wish I had more of the modded horses to share pics of, Champion Destrier and Arabian for example also have faceplates. Though I do have an unloomed Destrier, which is a whole new model so I might as well get a shot of that. You should get a shot of your charger up too, I see you riding around battle on it.
As for what the scabbard should look like, that's a good question. I guess I would just say go with something similar to Final_Boss' work on similar swords like the BS or HBS. Or maybe even take a look at the italian sword or short broadsword scabbards since they sorta look similar to the longsword, maybe you can take inspiration from there.
I wish I had any ability in this department I'd do what I could to help or have done it by now myself since it's been such a buzzkill without it. Maybe when you're done I could use the program you're using or something to make a darker texture version of it for the alternative darker pack from the installer. I'm assuming I could take a look at what the differences are with the scabbards between the two versions and adjust the brightness to something similar.
New (+0)Destrier Model