Thank you for posting these pictures. The originals really are simple compared to what some do today.
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These are Valley of Virginia rifles fairly early. If you notice on all three, the decoration is sparse compared to a later rococo carved Golden Age Gun.
With this said notice they all have moudling lines, beaver tail lock panels, decoration around the tang that corresponds with the beavertails. The Faber has some decoration on the upper forestock. You can barely see some of it in one of my pics.
Personally, I would concentrate of the decoration that's an architectural element. The stock moulding lines, forestock moulding lines and the beavertail lock panels. These are "simple" but need to be executed well.
Study early rifles from that period and region. Some can be very plain but nearly all of them will have the basic decoration mentioned above.
It's not very deep at all.