One problem with casualty markers to WM is that they aren't actually much use in the game. You only need to track wounds during a combat - and small dice seem to work better for this, than markers.
For other games were units carry their wounds around between turns, then markers can be very useful, and look really good on the table.
One thing I have thought about in the past, but never actually tried, is to leave a marker on the table for each casualty a unit suffers, which would leave a litter of dead around the table as the game unfolds.