Your program looks great. I have been destroying lumber like crazy.
I know that I have to pick the right size bit for the right size carving. My problem is what is the ideal looking bmp to start with. Could someone send me a simple drawing to sample? At least I could step in the right direction.
I wish I could give you a number, but there's no right answer. You've got several parameters that affect the output.
1) Relief dimensions. When you load a bitmap you must set the size of the finished relief.
2) The bitmap dimensions. Whatever bitmap you use has a height and width defined in pixels. The more pixels, the more accurite you can machine a part. There is some limit to this though, a 1000x1000 bitmap is no good if you're going to machine it to a size of 1"x1"
3,4) Toolpath stepover and cutter diameter. The stepover defines the distance between the parallel cutter passes used to cut the relief. Finer is better, but there is a point of diminishing returns. I'd start between 1/3 and 1/10 the cutter diameter.
The best thing to do is try a buch and see how the output changes.
Let me know if this helps,