In my opinion I wouldnt add a 3d background. You will be loosing some tank real estate due to the size of the background plus I think over time the algae and coralline algae will will cake up in the nooks and crannies and probably look worse than if you had no background. Plus you won't be able to scrape the 3d background or really clean it if you want to.
I have my tanks painted black on the back and you can barely see the coralline on it after a few months so I would vote just to paint it.
Now if I were doing a cichlid freshwater tank I would be ALL OVER that background, I wanted one pretty bad for my 125g but it would have been too much money. :-(
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.