Attaching rods just below the ceiling molding or too of ceiling if there is no molding and hanging long, to-the-floor curtains make the window look longer and more elegant.

Sorry or top not too of ceiling

Bring the curtains out on the sides further and makes sure yiu have a minimum of two panels on each side.
Fullness and length give a custom look. Always but always iron your curtains or have them professionally pressed before hanging. Use a substantial rod and if you the rod sags in the middle, use a brace right in the middle. These are the difference between a custom and great look and a mediocre look.

Here are some ideas. Hope it helps to inspire you

Try to find wider curtains as regular panel curtains don't stay together after a while.

It is nice guest room. Love the color and organization of whole room. And i think, yes, you need to get a better curtain. Long style from top to floor would works. simple pattern and warm color.

Hi---simple floor to ceiling off white panels for the windows. If I may suggest, switching the brass fixtures and art to a brushed nickel or chrome finish, painting the walls and trim, and adding a different rug. Look to your bedding for inspiration. Here's some ideas. Hope this is helpful. Good Luck!
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I looked at this again. The wall space is so small between the window side and the wall, that I would bring the rid and curtains to the wall on each side and if course floor to ceiling. Make sure you make them full with enough panels.

When hanging curtains especially rid pocket, make sure that they are evenly gathered and the small header is all pointing up in the same direction. It takes a little fiddling, but these are the things that make enormous difference. Did I mention press your panels. The wrinkles will NOT come out on their own.

Long day curtains (white) with long night curtains (blue or grey) from the ceiling to the floor covering the whole wall and the room will look awesome without any additional changes.

This is good representation of the wall to wall floor to ceiling look for a short window

Although, the have a built in and a short curtain here, you can get the idea of covering the wall space with panels and imagine floor length. Lol
Good luck and have fun putting it together. :)