Regarding the current vectorized VFD Artwork, I've noticed that, compared side-to-side, they sometimes are not very accurate to their source.
This is specially noticeable when looking at certain cartoony figures, which sometimes look like they've been drawn by using tracing paper over the original art (kind of how other artwork in MAME would look if it was replicated by hand, I guess).
I ignore how these are being made, but perhaps there may be some alternative way of creating more accurate vector files out of the originals?
I fear that this could be a problem that will be carried over to all future supported handhelds, and will be specially noticeable in those with more elaborate graphics, licensed characters, etc, so now that the ball is just starting to roll, it may be a good time to look into it...
LCD artwork scans and cleanups: https://mega.nz/#F!uFYSzK7S!U-lJon9jsqyoCX_3y7_KLA