It is ironic that your room is quite light so far yet you feel it is dark.

I certainly think some fun wallpaper would work - could you put some on the adjacent wall where Mr Buck stops here is? (see image below)- this would add some fun and validate his presence!

A nice cream rug would also help to add warmth and reflect even more light into the room

Try moving your furniture arrangement around so that opens up the room a bit. Could you manage placing a sofa by the window and then moving the armchair to the middle - basically opening up the closed shoulder gap that I see when I look as a visitor entering this room

Finally, for your drapes find some fun material (I think IKEA does this wood in fabric) so you could use that as your drapes as well. It would tie the room in together

Congratulations on your new home and all the best for this project

The closed blinds are causing the dark feeling. You could put UV film that is one-way (you see out, they don't see in) and then hang drapery panels floor to ceiling so they just cover the frame of the door. You have plenty of room for a stack back if you want closing drapes, but if privacy is not an issue, just stationary ones may work fine.

I agree, the room is bright but just feels cold. Needs some color.

The floor lamp juxtaposed against the buck head makes this space very interesting. How would you describe it?