As someone who worked design for a little while, here are some additional thoughts:
-You have a lot of neutral going on, which is great. The space has some really good bones. That means you have a lot of freedom in choosing what to highlight.
-Having said that, choose an accent color to highlight where you want eyes to go. This can be done through wall art, pillows, etc. Keep the furniture neutral and the space will maintain its size. A rug might be a good investment, to break up all that bare floor.
– I agree that starting with a clean slate is best. If you can, go room by room and remove the furniture. Then put back only the pieces you like. I also agree that plants will help cheer up the space and make it more homey.
– If you buy that foam, get something to hang over it. Curtains, a tapestry – that way you don’t have to look at the black foamy walls. Drapes would also help add a layer of sound-proofing, and if you buy a texture or pattern it can help with the art! Think of it like wallpaper.
– Remember: Art work doesn’t always have to be framed pictures (though those are nice). Mirrors, sculpture, vases full of flowers (fave of mine) – all these add depth.
– De-clutter the bathroom and kitchen. Try to keep uniform color in the kitchen, and add some color to the bathroom.
If you have any questions, let me know! I love this sort of thing 🙂