Rather than making specific suggestions, I’d suggest that you take a bit of time to work out what YOU like, because taste is so personal.
Go to the newsagent & get a few home decoration magazines - the sort that showcase improbably lovely homes ðŸ˜. Country Homes, English Country Homes etc. (Focus on the magazines that show pictures of actual homes, not just ideas and adverts.) Then sit down with a cup of tea & some glue and scissors and a scrap book. Flick through the magazines & whenever you see something you like, cut it out and stick it in the book. It could be a room, a colour, whatever. At the end flick through your pictures and think about what makes you like them. Is there anything they have in common? Colours? Are you going for rich or light colours? Single colours or mixed? Patterns? The way colours are repeated through the rooms? Types of furniture? That helps you to see what YOU like which may be completely different from what others like. I mean some people like single small pictures in a wall, others one big picture, others a mix. We’re all different.
Also worth thinking - when someone comes into the room, to what part of it do you want their eye to be drawn? (I usually think the opposite area of the room from the door, to make it seem bigger, but you might prefer elsewhere). How could you draw the eye there - a colour, a big picture, a big plant? A mirror? How does the eye get drawn to certain areas in the pictures you liked?
Another thing I find useful is material samples. Clarke & Clarke do a velvet called Alvar which comes in loads of colours. You can get small samples from a website for £1 each (first 5 free). If you get say 10 of these it’s really helpful in thinking about what colours you like and how they look in your room (whether or not you actually want to buy any material!).
You can also of course get paint samples to try out colours but they work out more expensive. I have used the F&B pre-painted sheets before but they are £3 each and inevitably I end up hating most of them.
Thing is that if it were me I might well do something like paint your room a dark rich brown with red and lilac somewhere - but that’s because I find those colours soothing in a bedroom. Others may well hate them! So I would try to work out first what you like.
It’s such a nice shaped and well lit room, I hope you enjoy decorating it!