This might seem a silly topic for this forum-unless you are building an intact building or undamaged part of a damaged building and you want to avoid building an interior behind a window.

What sort of inside window coverings were used in ages past? Curtains? Pull-down shades? Venetian blinds? I've seen old buildings with these, but in many cases they weren't necessarily the originals.

I guess curtains are your safest bet :




Frenchy

Ola Tom

This is just a matter of Anything goes. And it really depends on your patience with scratchbuilding. Pretty much every type of window covering have been around for a long time. Rolling curtains made from reed were in use since the Egyptians. Venetian blinds were patented in 1700 something but were already in use for a long time. Pull downs made of cloth existed since the mid 1800's and were the cheapest to produce and therefore pretty widespread.
Curtains have been around since the cavemen really, to keep draught out of caves.
Only exception is the vertical slat type of blind which is pretty new.

So yeah choose one and you're pretty safe all round