Light is a central consideration in building the light box.
The best way toward even light distribution even with good dispersion sheets, is to have multiple light sources. I recommend placing them at the same distance apart as the depth of the box. It would be possible to pack the box with light fixtures, but this is expensive and generates a lot of heat. It also may make the light too intense to be comfortable to work with. If you can control the general lighting of your studio and you can turn it off or down, you will not need such intense lighting in your box.
An alternative, but more complicated method is to build the light box with baffles so the light is never directly under your work. Commonly, this would require the box to be built wider than the glass upon which you will be working. The light reflects from the sides and bottom of the box to give an even light. In this case, the single sandblasted surface would be sufficient to disperse the light and keep your eye focused near the surface of the glass or cartoon on which you are working.
You need to have daylight corrected light sources for you light box, especially if you are doing any glass selection on it. Fluorescent tubes are easily available, but other light sources can be used if they can be found in daylight colours. Fluorescent tubes do not generate much heat and are available in daylight corrected colours. So these are the common choice.
You still need to have ventilation to allow the heat to disperse, though. Ventilation can be provided in a number of ways ranging from drilling holes in the sides, to providing a slot in the side or bottom.
You need to have access to the light fittings to replace bulbs. It is easiest if this is by removing the glass top. You can provide tabs on or under the glass to lift it with, but these often interfere with other uses. You can use the ventilation holes if they are high on the box to stick a lifter under the glass to be able to grasp the edge. You can have a removable section to the beading that holds the glass top in place. You can provide a couple of finger holes at the top edge of the box to enable more direct lifting of the glass without disturbing any of the box fittings.
Another important element in getting the maximum amount of light out of your box is to paint the inside white. This should be a matt or at most silk finish. Any glossier finish will produce bright reflective areas. Shiny surfaces such as aluminium foil also produce these unwanted bright areas. In fact, a matt white surface gives more apparent light than aluminium foil in the light box.
The lights should be wired in series so they all come on at the same time. It is of course possible to have a switch for each fitting, to vary the intensity of the light for the work you are doing. This does add a bit to the expense, but may be valuable for your way of working.