[Arran]

As long as you used lacquer to finish with you can always go back and use a die based toner over top if you need to. You can also go over top of the lacquer with grain filler if need be, as long as you let it cure long enough.
I like to use veneer to patch veneer, sometimes they used special cuts to get a given grain pattern, there was plain, rotary, and quarter cut veneer, and they would often use different parts of the tree like the stump or in the crotch of a branch to get a given effect.
Regards
Arran