We cannot bevel the edges of parts. However, note that the laser cuts at a slight taper, as noted in our "laser cutting capabilities and limitations" page:
The laser cuts at a slight taper (1-2 degrees) since the laser beam is shaped like a cone (it gets focused from a larger spot to a small point). The tapering causes one side of a laser-cut part (the side facing up during laser cutting) to be slightly smaller than the other side. The taper is almost unnoticeable in 1/8" material; the thicker the material, the more noticeable the taper. When using laser-cut parts such as wheels or gears, you might need to position the parts in an alternating pattern so that the tapers "cancel out".
I hope this helps; please see http://customlasercutting.com/info/capabilities for other things that might affect the design of your laser-cut parts.