Tsk tsk... Art at the least is something which resonates with you, for any reason, great Art is a bit different..... Buy a prepared canvas and some colours you like and have at it. Then hang it up on the wall.... I would suggest a large horizontal canvas close to the width of the sofa for that wall.

For the best ceiling fan designs try Urban Lighting, they have a couple of shops in Sydney and some very unique designs in both traditional and contemporary. I have a deco house too and am looking at their lighting products for our new extension. The lines in your ceiling rose are sharp and square so I think a modern fan would look great, but luckily with deco you can go either way. The link is https://urbanlighting.com.au/collections/fans and below are some from their modern range which may compliment but not compete with the detail in your ceiling rose:

I'd echo most others views -- personally , I could live with the aircon and the lights , but the furniture and the mirrors would go ! Again , just personally , I don't have a problem with the mirrors sizes , it's the silver that doesn't suit . I'd go approx 20% smaller mirrors , BUT with really nice wide sculpted dark wooden frames , and lift them a bit -- they almost look like they are sitting on the mantlepieces at present -- lifting them would show more balance IMO . Lounge suite I'd go big , boxy , good quality bright red leather . A modern corner suite would probably suit , or one with a moden interpretation of a chaise , but in big boxy red leather . Or maybe a more classic looking buttoned leather suite , just not in brown -- that would be too much brown . Red or white would work well . The dining suite could be a large 8 seater wooden table in darker brown ( that mahogony one clashes to me ) , or glass top and stainless if you want to be more modern , and modern red chairs -- several styles would work , depending on what table you choose , and how modern you want to be . And for a more modern twist on the windows -- wooden slat blinds -- I have done very similar in my own 95 year old place , and it works well ! My place is similar , although it doesn't have those higher picture rails -- my place has carved rails approx 1.2mtr above the floor level , and Rimu panelling ( a NZ wood ) below that -- has that 'gentlemans club' feel . I did the walls above that in a mid steel blue in some rooms , a grape colour in others , english cream in a couple , and an earthy orangey-brown with white gloss tiles in the kitchen ! And in most rooms , I did a feature wall , wallpapered in complimentary colours to the other 3 walls in that room ! Strange sounding I know , but it works ! In the larger rooms and entrance foyer , I have large gold waterfall chandaliers , the other rooms I have gold curved light bars with 4 to 6 led spotlights -- all with crisp white ceilings similar to yours , and art deco inspired ceiling roses and architraves . I love the mix of classic and modern , with a twist of class

It’s lovely, Alice. Great choice of light fitting, very deco. And what fantastic floor tiles. Always a little tricky to modernise without losing the historical aspect but I think you’ve done it. So pleased you kept your window, too. Well done, you must be so pleased