I think painting the walls does a great part, really shapes the room. But if thats not an option, you could get fabrics and hang them. In Europe/Germany there's a great shop, kamandala.de. And get flags at your countries antifa stores.
Another important part is indirect lighting. Really one light on top is absolute shit if you want it cozy, so some RGB Led bulbsand adjustable standing lights are IMHO great. Combining leds on wires with fabric/flags is great to let them shine at night. Works great on plants, plush, decoration, literally anything.
Personally I love photos, so I made a photowall with photos I took of cute plats, cats, friends and whatever felt neat to print+hang.
To be fair my vison of rooms is from videogames, specifically life is strange, buuuut whatever.
LED strips or twinkle lights behind a very sheer curtain against a wall could work well!
Here’s a good pack of twinkle lights I just found on Amazon, although I’d check the length of your wall if you want it floor to ceiling :)
I (try to) stress less about my daughter's gear than I do my own, mostly because she will grow out of it. Plus, my number one goal is to make it fun (and safe) rather than get the best gear. She doesn't care, so I try not to care on her behalf. (There's probably a lesson there for me....)
Backpack: She started with an REI Tarn 18 when she was 7 or 8. She got really excited about adding patches and really making it her own. (I tried not to fret about all that extra weight!) It's not the pack I would have picked for me, but it was durable and cheap and she loved it.
When she turned 11, she got a REI Tarn 40. I spent way too much time looking at the various kids packs that were available. I was strongly considering the ULA Kid's Spark, but in the end stuck with the cheaper REI option. Like the Tarn 18, it's durable and cheap and she loves it.
Shelter: At first, I tried to set her up in her own shelter, a Big Agnes Copper Spur something or other, while I used a hammock. That was fine at first, but she joined me a little after bedtime. Now we use a two person shelter (a BA Fly Creek). I highly recommend adding fairy lights or something similar (e.g., this).
Pad: She uses my NeoAir, regular size because that's what I have, and I use my Z-lite. I'm pretty sure she would be fine on the Z-lite - she often rolls of the pad anyway and just sleeps on the ground.
Bag/blanket: Depends on the weather. We car camp a lot and have a variety of options, from a fleece blanket to a down mummy bag. I usually pack an extra layer because I worry about her being cold and you're supposed to pack your fears, right? She's never needed it.
Clothing: For worn clothing, I got an REI kid's Sahara shirt on sale. She also wears leggings of some type, sneakers (we both like Saucony Kid's Peregines), and a ball cap. In her pack goes a hooded fleece (no specific one), some fleecy longjohns we found at Target, warm hat, and gloves. We also bring her winter coat and a plastic rain poncho, as necessary.
Extras: her own Swiss Army knife, mug, spoon, deck of cards, headlamp, toothbrush, compass (not necessary but fun), whistle, inflatable pillow, Smartwater bottle, pee towel.
I usually bring one set of trekking poles. I run hot and cold on them, but they're handy at stream crossings and other situations where a balance boost is called for. Usually I carry them and hand one over when she wants one.
Oh, also bring lots of snacks. Whipping out a surprise snack at the right moment can make all the difference between a death march and a romp in the woods.
I hope this link works, it was a 12 pack for around $13. They're battery operated and very bright. fairy lights on amazon