Woah, that’s a sweet mobile! The walls and ceiling in your office have a spacious, industrial look to them. The only colors in there so far are the white walls and the red mobile, right? I think this one from Crate and Barrel might match. But it might look better if you got something more old-fashioned like an Oriental rug. If you pick up the bright colors in the mobile in the carpet it might be an assault on the eyes, and you guys have to work there. If you got a monochrome carpet, your office will be nothing but solid colors. Oriental rugs, especially antique ones, seem to fade over time to subdued browns and reds. I like the juxtaposition of antique furniture in a modern setting, and patterns with solids. Ikea has a nice version, and it might feel better than buying an antique rug. My parents used to have one and the material is weirdly bristly, and not great for sitting on.
Edit: Now that I look at the picture again, maybe modern isn’t the right word. From the wall, it looks like an older space that was refurbished, so maybe minimalist would better describe it. I always wished I could live in an artist loft that used to be a warehouse or a factory or something.