You can buy an outdoor carpet / rug or artificial grass for the concrete slab. Buy a piece that is almost as large as the slab.

Hang a big mural on the brick wall. You can buy a large piece of sheet metal and have the edges folded over ( buy it from a sheet metal fabricator ) and paint it with bright colors that go with your interior decor. It should be lightweight and you should be able to secure it into the brick wall without doing any damage.

Hang several strings of outdoor lighting over the top of the patio. Hopefully you have an outdoor outlet or wall light that you can use for electricity........Otherwise look for solar lights on a wire.....I know that IKEA had them available a while ago, and they do exist. You can also look on Amazon.

Place your chiminea in the rock area...........You might want to replace those rocks with new colorful glass ones that you can buy at fireplace stores or just about anywhere these days.

Finish up with a few nice outdoor chairs and a table and you are ready to entertain.......

We definitely need to do something with the cement slab, that's for sure. I was considering power-washing and painting it initially, and adding more gravel around the outside. I never thought about using some other kind of colorful fill though. Is there a site or image you could reference that has the glass stones?

I would power wash the concrete, then fill the area around it with Mexican beach pebbles. Some plants in colorful pots, your chiminea, a few chairs, you're good to go.