Here's my slant. This is not good, but possibly can be. The WB is off and casting a yellow hue. You've probably exposed too long which is causing the blown details of the cozy fire and smudged all your tree lights. Heavy shadows from the mantle ornaments. The tree looks as if it's about to be toppled (using the wide end of your lens?). The framing of the doorway interferes and competes with the top of the tree. The second room (with monitor) is a miss and totally removes the essence you're trying to portray.... Christmas decs.
Some possible remedies.
- Put your camera in portrait orientation on the tripod. IMO, what is important is the tree and mantle.
- Move around ~90° from where you are now. If the mirror above the mantle is still in view, replace it with a wreath.
- Place a cover over or turn off the aquarium light. It's throwing a blue-green light into the scene.
- (Debatable) Set camera to Av priority, with an aperture of ~f/8. Set flash synch to ~1/125 and flash mode to TTL (You have a SB-600, right?) and have it off camera.
- Bounce your flash everywhere... the ceiling, the wall to the right, the wall behind, off some crumpled foil, through a sheet...... be creative.
- Meter on the tree. Meter off the fire. Meter several spots.
I don't know, there's more but these are just a few thoughts. Try one or two of these and see what you get. Let me know if I am full of it too.
Good Luck.