I very rarely engrave floors, I must admit. Or indeed walls. But that's because I (usually) don't need to. Fully smoothing noble rooms usually does the trick, and carefully distributed masterwork furniture (at least some of which they're getting anyway, either for room definition or as part of their demands) buffs them up.
But I did engrave one entire wall and the adjacent floor of one set of noble rooms on one fort, as the easiest thing to do (I'd done a lot of engraving as part of the megaproject I was running, and had very little left to engrave that was not still waiting to be exposed, so I had a number of legendary engravers that would only be doing more trivial things), and I did that symmetrically across the whole Noble-only accomodation/office/dining block that I had made in that particular part of that fort, so it overkilled a number of room requirements and caused haughty thoughts in various ones about some having better rooms than others thought they should have had. Which I took no notice of.
(Given different circumstances, I might have removed the walls and rebuilt them/paved the floor with precious metals, but I'd only gotten a basic metal industry up, mostly geared to making electrum 'spires' for all the obelisks, to supplement the electrum I was gradually accumulating through trade.)
And, yes, it looked ugly, while I left it visible. Can't blame anyone for not wanting to do it in the first place.