I would place the piece of artwork/sculpture centered on the vault, place it high enough on the wall that the hutch below doesn't matter in regards tot he art placement.

With that said are you wanting it to reflect their girls styles or yours?

phununthesun has a good idea.

You could more the floor lamp behind the chairs, have china hutch start just right of the thermostat and the lower hutch behind the sofa. Than you would center your artwork above the furniture piece.

you can also find a tall skinny piece of art and have it sit on the right side of the lower hutch leaning against the wall.

Move the blanket cabinet toward your other one, like shown above. Add floor plant in the corner. It will disguise the thermostat slightly. Plant killer? Try Nearly Natural Fiddle Leaf FIg tree. (Shown) Put tree in a bigger basket. Fill it with newspaper & top with dried moss

Sativa McGee Designs This is a smaller childrens area. Leaning art may not be a good idea.

Narrow piece?

Or centered to the high point of the vault, as suggested by Sativa?

You're a good uncle.

I think it would look fine to hang artwork off-center toward the right-hand side of the hutch, just choose something taller than it is wide. The height of the lamp will balance it so it won't look odd. If it doesn't offend you masculine sensibilities, I would choose artwork that echos the colors of the blankets. I'm sure your nieces would be happy to help you pick something out...

https://www.greatbigcanvas.com/view/spirit-garden,2408269/?s=eparNXLhb2Amz821i0oLl9cS5g5AYMGqJXDhfFIEw4YHlRC3hsH4fQAHdpSID

I think a nice family photo wall collage would be nice. You can choose the same color black frames but of various sizes. Fill them with pictures with you and your family or of special places. It will also make them feel loved and give them something to talk about. Google will have lots of ideas on different photo collage ideas.

your balance is so off can you put the dark pieces somewhere else

Standing and cheering for you! Those are lucky girls to have you in their lives.

How about switching the position of the two cabinets? Place the tall one close to the Nest and the shorter one to it's right. I prefer the look of some separation between the two. You can also move the floor lamp to the left of the Nest (don't you love those thermostats?!

I might look for a lamp that could move forward on the chest enough (without danger of toppling off) that the shade just hides that thermostat. Place it just a couple inches to the right of where it is now, or move the whole chest to the right a bit. It won't affect the functionality, esp if you use an LED bulb = no heat. Then look for a large piece of art, or a couple of stacked pieces to fill in over the right side of the chest, as shown above.

Another idea is a gallery wall incorporating the thermostat:

I would trade you those beautiful folded blankets for the star wars lego decor my grandson has decorated my house with!

eta: I was just looking at it again and think Cyn's idea to switch the cabinets would work. You could then place the floor lamp in front of the thermostat and just ignore it.

I like hoovb's advice, except rather than art, you could put a chalkboard/felt-board/pin board and use paper cut outs or felt stuff to let the kids walk up next to the hutch and design "art" for the living room. That would keep them busy too, and if it's confined to the one area you can put something even above that, like a clock and some photos that draw the line across the wall entirely and above all of the things.

Or this:

I have no doubt you will get fabulous design advise here. I just want to say that it sounds like you are providing such an incredible loving place for your nieces. I hope the experience is as fulfilling for you as it is for them.

And, I actually think the rainbow blankets look really cool in the hutch! Not something I ever would’ve thought of, but it it makes an awesome design feature! Own it!!

You rock!

I'd do a large vertical piece centered on the vault. You could ask the girls' opinion on this one....or maybe not.

https://www.greatbigcanvas.com/view/moonlight-unicorn,1053384/?s=HOzy15ktBO9b7orDHG9W2rc6WjFzOkzoiYJGYkb6fzd60QzxbsqaCzEWidrPaEk

It looks like you just need a piece of art over the blank section beside the lamp. That should do the trick.

i don't disagree with any of the advice but why don't you just hire someone to move the thermostat-- it's not a very big deal.

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