If you ever wanted to consider it, head over to me3explorer.freeforums.org and get
me3explorer . It can be time consuming work but in the case of the house style stuff, you maybe can't easily add items, but you could consider re-texturing existing options.
I didn't think I could make a mod to change audio and subtitles but in the end I could. Granted, with a lot of help and 150 hours. But textures...those don't have to be as brutal or time consuming. Although Ottemis or Smartek may slap me across the face for saying that.
For the piano...that gets more complicated. I'm guessing there's a trigger in the pcc file for that when Liara visits so I'm not sure how that could be added in the general apartment pcc file.
Ignore my tech speak. If you want to go for it, read up on the me3explorer forum and see what you think. You might surprise yourself with what you can figure out. Back up your game files and give it a try.