I've used planks to make a large two story deck and argonian reed tents and canopies to cover the top one.
I have also used orcish bars to cap the front of a second story area to make it look more finished, it really looks great with structures that have dark wood already.
I've built my own fireplaces with stones and statue bases because Daggerfall Overlook does not have any, unfortunately.
I have censors or incense placed in areas that I want smoke. For example, you can put them in fireplaces, use them to make a hot springs, or place them inside furniture items to make them look active/animated (e.g., trophies and pvp ballista figureheads). I've even used a censor in the Vvardenfell Scale Model volcano (thanks for the idea, @Livvy!)
Additionally, cages make great bank vaults and the achievement item Serien's Stand makes a nice coffin stand or fireplace chimney.
Awesome job on that waterfall.
I was planning on making one myself in a different house also using skyshards but I'm waiting on some of the new items to come out with next patch, they will really help make it look even more real
One thing also to note:
Too many animated light sources; candles, sconces, fire-lights of all kinds, can sometimes glitch out, resulting in the lighting working but their "fires" missing until turned off and back on again.
This appears to be a client-side rendering problem which I havent quite determined the boundaries for.
Some guests say it renders just fine, others say the "fires" are missing from various light sources, though which sources display their animated fires do not appear to be consistent between clients.