Hi, I'm putting together some field tospruce up my Napoleonic battlefield, but I'm not sure of the scale. What size should I be aiming for? Cheetrs.

Fields could be quite large or teeny tiny depending upon the location.  Also depends on your ground scale and board size.  I'd go for something that makes sense with your rule set and what you are trying to achieve with the fields.  If they are purely visual then "what looks good"  should be your maxim.   Having said that anything large than 12" will become unwieldy and smaller than 4-6" will be too fiddly so I would go for something between those two.  If your area did have small fields with hedges or walls between that would break up your formations (eg a Battalion in line won't fit) I would suggest modelling them as a whole and counting the area as rough ground.