Okay so given the mirror and the velvet, I'm going to suggest going in more of a French direction in here.
There are daybed covers that you can use that are more tailored.
You can do a cover and add pillows along the back (you have to be generous with this so that it looks inviting--big, full pillows) OR you can keep it simple and do bolsters on the ends if you don't want to hide the back.
https://www.amazon.com/Madison-Park-Rosie-Daybed-White/dp/B07DHKWNY6
https://www.wallpapermatte.com/ (top 2 pics in this link)
Don't forget you need a throw....
Since we're going in a French direction, you can get a ladder blanket holder for the right of the mirror...if you can, scour your local secondhand market for patchwork quilts (near me, they're not very expensive...)
Put the plant on the floor and move the stool to the front of the radiator...that's a nightstand (go on another search for a vintage clock and a couple antique books).
I would have white semi-sheers in here....linen or voile...