I think painting the walls lighter and brighter is the right move but don't be restricted to white necessarily - although that would be the safe option and you know for sure it would work! You could introduce a contrasting colour on the ceiling if the walls were white obviously dependent on your furnishings and other colour choices. How about a soft grey or "greige" as an alternative to the white? Finally, you could introduce a dado rail at approx 1m from the floor - painted white the same as cornice and ceiling and then paint the upper and lower sections in contrasting colours of say charcoal on the base and white above or 2 shades of the same colour.

Think of introducing a contrast to the white - black being very contrasting, white not being a contrast and soft grey being somewhere in between (but possibly not quite enough, in which case you may need to go for darker shades of grey) . The analogy might be framing a picture or piece of art- If the canvas is really white, you wouldn't choose a white frame. Or putting on eye makeup- if you choose to put a colour on your lids and don't include eyeliner or mascara, your eyes will lack definition ! What colour is the roof ? Also ,have you chosen the white of the exterior yet because these two factors can help in your decision process.

strip part of the brick and mantle back to orignial if the exposed colour lines up with the room, strip the whole thing. Looks so well crafted not to pay respect to the past

You should do a google search of “ teal headboard “ and there are many images which should help . Similar shades to those Dulux ones will be there . When your bed is ready , paint a few shades in strips to see what works with your bed head and carpet .