I know Gantry Co. has been brought up before on this forum but I just to throw some more recognition their way.
Lou Saye at the GantryCo.com has again supplied me with a great 3D file and the detail and crispness of the results are astounding. Lou has many pieces for sale and will even custom make a file for you. They are a great value considering their quality, uniqueness and the fact that you can use them as much as you want.
Some common thoughts on 3D engraving is that it takes to long and can not be done economically. I believe that as newer technology arrives, engraving speeds keep increasing and with Lou Sayes artwork that many people will be able to offer this service for a fair price to their customers.
Take a look at the latest file from Lou. I engraved into 1/4" Maple.