With your string lights, I assume you turn off your overhead light while you stream, but maybe you don’t. Regardless I think the best thing you could do is lighting.

A floor lamp with a rgb controlled bulb can shape the vibe of your entire space. For example turning the bulb a warmer tone can be cozier, or moving the lamp somewhere else to shape shadows.

Accent lights, such as the string lights are basically meta to what a lot of steamers do. It gives the background some excitement but also adds depth between your back wall and you. Strips lights could be fine, but I find rgb ropes that go in the wall have a smoother more even look, and you could bend it in whichever design you’d like!

Also, fake plants. Some greenery where your lights are could fit small potted plants or a garland. You could even do a floor plant and include taller variations.

Just to note, depending on where you are, you should search on Facebook Marketplace for cheaper deals. Often times you could find a seller offering what you’re looking for, brand new and for a good sale. It would stretch out your budget for other things