Looks pretty good really,
Try a 4-8% step over (translates to about 0.0025"-0.005" ridges) and try a square end end mill. You actually don't need a ball end unless you have features that require it.
This to me looks like a height map generated by an image with a lot of contrast where the edges between the circles and the background a very crisp. This type of image doesn't really require a ball-end mill and will cut down on ridges on the back of the plate.
Now if you decide to do something complicated like a portrait then the ball end mill would be necessary.
What software are you using to generate the gcode?