I assume a cable hangs from the tray to the desktop? I suggest adding some climbing vines, with pots, so it looks natural. You can also add a few spider monkeys to go up and down the cables, and their poop will fertilize the vines after you scrape it off everything??
The basic problem with trays is the cable from tray to desk.
If you used a dropped ceiling (aka ceiling plates), you could have a high BW bidirectional infra-red network from overhead to desk. In fact, with a few bidirectional emitters you might cover the office very well with even less intrusion, http://www.fraunhofer.de/en/press/research-news/2012/october/wireless-data-at-top-speed.html
With IR reflectivity on all surfaces, coverage will come easy. The surface could look different at visible wavelengths for aesthetic reasons.