This is not to be confused with Shadow Weave but is a nice treadling option to try with an overshot treadling. This is one that Barbara Miller, my mentor, taught me during Teaching and Learning through Correspondence (TLC), 1993-1994.
As an option, try Mary Snyder's suggestions for Shadow Fashion.
Shadow Fashion/Barbara Miller
Pattern and tabby
Weave tromp as writ or another treadling. Use tabby for the pattern thread and pattern thread for the tabby.
Shadow Fashion/Mary Snyder
Pattern and tabby (2)
Use 2 picks of tabby between each pattern pick in a finer yarn, one as the warp color, the other in a contrasting color; this should be a good contrast with pattern color.