you don't need the crowns. you can build some very nice fireplaces with materials bought solely with gold. not saying that it wouldn't be awesome to have an option to buy just prebuilt fireplaces. and stairs. etc. it would rock if ZoS added them, especially for gold, or crown option. just saying that you don't need crowns to build one. a tiny bit of patience - yes, crowns? no.

You can build a fire place and buy a flame to put into it. My forsaken I suck rough cut stoned into the floor and brought 2 fire logs with a good amount of fire and placed em in the middle giving a sunken fireplace in the middle of the room.

It would be great if we had a fireplace in game; but, I became impatient and built my own using 2 (3 if corner) statue bases and Serien’s Stand. Good luck

You can make decent fireplaces with ayleid benches/thrones/tables + any fire or brazier. Tables and benches are craftable, and thrones are sold by Coldharbour achievement merchant (though theyre pricey, like 50k each).
2 upside down ayleid thrones, 3 tables, firelogs (flaming) and one bench: 2 benches, 1 table, firelogs (charred), statue base (square): I took firelogs from my Cliffshade house which I use as furniture storage, theyre also available in crown store I think. "Khajiit firepit" works fine, too (its craftable).

Orcish brazier, smoldering is also a good substitute for the firelogs, if you don't want to spend crowns. Sink it in the ground so just the lip of the bowl shows (matches the stones) - can also push it back a little to make a semi-circle.

Here’s a aleyid benches sunken fireplace
4 benches and 2 fire logs cost 6 slots.