Another sample image for you guys to look at. Personally I like the parchment background (though I'd want the final version lighter), but the artist doesn't. Is it really that bad? If there's enough hatred I'll rethink it.
USPCC is urging me to shrink the design by 3% in order to avoid registration errors, though I worry that will make it even harder to read the indices when fanned.
(Oh, and picture the yellow areas in the border as slightly metallic gold.)
I think you'd be better served with white on the edge. At the least, if you really want the parchment look, then make the border on the back the same color.
Take USPC's advice re preventing registration errors! In fact, err on the side of caution and consider a percentage point or two SMALLER than what they want. If you're concerned about the indices, beef up the thickness of the lines in the font without actually making the letter bigger (or at least not much bigger). Either that or make the gold the background color for the letter and make the letter in red/black - that would stand out nicely and look almost like an illuminated book.
I think that the picture has too many details. Most of them will be lost and become "mud" when printed in the actual size.
As for parchment, I like it but I think it needs to be lighter.
Just an opinion though...
The banner's size is okay, medieval manuscript illuminations didn't pay much attention to the right proportions.
For me, it's that the banner is at the end of a sharp weapon that's sticking out of a castle window! But it's nice regardless of what I think, really. The art is gorgeous, and Lotrek is right in that medieval artists weren't the most scale-accurate in history.