I would take the small pieces down and perhaps place a large piece on the wall you see behind the sofa. You've got a whole lot going on in this area. If it were mine, I would take everything down, edit to what I absolutely love, and reposition one thing at a time. Open space is okay and doesn't always need to be filled.

I've used Saatchi Art ( https://www.saatchiart.com/), which has art in a variety of sizes at a variety of price points. If your budget is more toward prints (though depending on the medium and the artist, original art can be pretty affordable), Great Big Canvas (https://www.greatbigcanvas.com/) or iCanvas ( https://www.icanvas.com/) sell large size prints in a variety of styles. Also, give IRL art shopping a chance. Galleries, art fairs, or the rotating artwork at you local cafe give you a chance to support local artists. I have many pieces from a local studio that provides space and services to disabled adults. There are also student art shows. I know it's more work than the internet, where you can look at hundreds of pieces in an hour and easily filter by price and size, but local shopping is rewarding and supports artists directly.

Wall hung items should be centered 5' above the floor or hung 5" above a piece of furniture. The furniture under them should be 25% wider than the hung item. The wall behind an item should be at least 25% wider than the item. That translates to: the picture doesn't work there. It loses all its presence when crowded like that.

It is a wallpaper, but the website isn't active anymore. I didn't have much luck with the exact one, but this is similar. https://www.etsy.com/listing/971072425/3d-abstract-traingles-wallpaper-mural?gpla=1&gao=1&&utm_source=bing&utm_medium=cpc&utm_campaign=shopping_us_c-home_and_living-home_decor-wall_decor-wallpaper&utm_custom1=k_744eddc564711c38c290bd9c6594d2b6_k&utm_content=bing_319895457_1302921427446871_81432615571304_pla-4585032209645604:pla-4585032209645604_c__971072425&utm_custom2=319895457&msclkid=744eddc564711c38c290bd9c6594d2b6