This must be the easiest and best to convert to a casualty for Medieval fans:
In the Strelets Medieval Levy set 1 M005 in the "Figures" photo - first row first figure on the left (with club). This is the target. Cut off the club do not use the shield. Bend at the knees to lean backwards. Small cut under the neck and bend head back slightly. You can leave the stub on the figure for the shield as a crossbow bolt (in the midriff -100% fatal in those days). The expression on the figure's face is so good for this conversion.
The fourth from the left has potential as well.
I agree that there should be casualty sets. In my opinion the Strelets Charge of the Light Brigade walking/riding casualties are some of the nicest figures made in plastic and deserve a much wider use for other periods. If they were sold as a separate set (not in a big box )I would buy lots- I am sure others would. Massima Costa's pics of his excellent conversions and paintjobs in parts 1-4 show how good they are.
No problem for your mistake, if you wont notice regard my casualty conversion send me a mail, for the position and drammatic move i inspired to classic picture. Sorry for my english language. I dont speak very well english.