How can I fix this hole creatively?

Storage......add shelving and nice doors with complementary door pulls. Can never have too much storage!

Solid backing and a nicely framed painting? Secret hidey hole behind?

A mirror or art piece. Another idea is to drywall off he area.

revolving turn table, small Christmas tree, small framed family photos as ornaments, hang fairy lighting on back of frame

I would put a large picture there seeing how you've already got the frame. Put a couple of hinges on one side so it opens like a book. If it doesn't have a bottom to it, make one with plywood & insert it behind the frame. Use it for storing valuables, documents, important papers, etc. It will be a hidey hole for secret stuff. I'd also put a small fire-proof lock-box in there for money or other flammable valuables. Only you & your immediate family can tell it's there. To everyone else, it only looks like a picture with an extra large frame. I'd paint the frame too to match the picture to blend in better.

Hi, Mary says...

Each Winter I just stand a big pot plant or vase of silk flowers in mine...

BUT...I googled and got the below site...and there are oodles of others...You may want to get the hole in chimney area covered...just get approx measurement and jam piece of ply/? up there...watch out for Santa tho'

https://www.houzz.co.nz/photos/query/unused-fireplaces/nqrwns/p/8

p.s.

could look up Alcove ideas too...I think they are really attractive...Mary

Hang LED mini lights inside the space, then cover the "hole" with a cellular pull down blind. This would make a nice soft lighted area during the evening, and give 3D depth to the wall space.

Can you attach a pretty piece of fabric to the back of it? Or mount a picture in it?

To me ... coziness is key to a home as well as welcoming colors that bring warmth and relaxation. Objects of design should be felt as well as seen! It's so important to have a place in your house which makes you feel good in anyway and every way possible.

A nice old antique stained glass panel rested up against the corner like the frame is would be a GREAT way to add charm, color and warmth. (stained glass can be heavy and very fragile so i would most likely hang it instead. looking out for those studs or beams which will hold the weight of the glass . There are also special , decorative hooks that have an anchor that goes in first to secure the weight. The older more intricate designs and colors are more expensive when it comes to stained glass so let's protect your investment! ) It would need lighting to brighten that dull corner. Overhead lighting is uncomplimentary to just about everything unless your getting your teeth cleaned!!! Up lighting would create to much shadow drama. Lamps are my prefered method of lighting because there are so many styles and types to compliment just about any room and decor. But our method for this job is backlighting! We want that Glass to show its brilliance and personality as well as making a statement to the room and the eye were capturing. We are also creating a "feel" or "tone" if you will ............

After its hung up the way you want it ( positioned as in the picture or similar since it might be a tad longer , shorter , wider, etc....) get some string lights , LED , incandescent , christmas, colored, clear, -it's up to you- and dangle or web lights behind the glass so that only the stained glass illuminates. ( you can go to any hardware or art store and buy those plastic sticky hooks that when you don't want anything hanging anymore you just peel the back, hooks come right off and walls are not damaged * or * just screw in your average small metal hook) You don't want to see any light peeking through the corners!! If you don't have an outlet near the corner your decorating then you can use a grounded extension plug. They come in white, brown, etc..... to match your walls or floor. you can also stabilize the extension cord with colored painters tape. We don't want anyone tripping or bringing down all that hard work! Not to mention the mess !!!!!

I also like to use old books and low light/maintenance plants like Philodendron to decorate around the glass. It adds a real nice welcoming touch and complements one another beautifully!! Plus it will hide any light poking out from behind the glass.

Plug it in ......

and ..............

......................Awesome isn't it !?!?!

What was a dark unwelcoming unfunctional corner of the room is now a welcoming eye catcher that will set the mood right no matter the time of day or the time of year.

Enjoy

Cheers.

Shelves might look nice, make whatever height you want then you decorate seasonal if wanted..

Ps- love Santa legs hanging out. Too cute!

How about a mirror or a painting?

Mirror tile.