Currently there's only one border available and it clashes with all the backgrounds.

Either adding more and/or the possibility to remove it.

Adding more proper borders is unlikely as we rely on Blizzard which doesn't have those in their files, but I agree that the border clashes badly. I might add the default frame border as an option (I seem to recall no border looking pretty bad too).

I am currently using the documents for some custom item properties and less for just a parchment as a letter, so as long as it looks alright it's still a good option to have.

And since you don't provide anything more that there is in game, I'll live with it.