With a sleek contemporary desk such as you have, it's usually best to keep accessories to a minimum on the desk. A simple chrome or colored desk lamp could be added. For bookshelves, you could place one end of the desk up against a bookcase, similar to what you see in the photo below. If you have an Ikea near you, their Billy bookcases with the added height units would be ideal.

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Thanks for your input Carolyn!
I agree with you about keeping accessories to minimum (that's why I pretty much went off the small book shelf idea) but I'd still like to add something beyond the desk lamp. I really like the placement of the bookshelves on your photo, although I personally prefer Ikea's Kallax (prev. Expedit) series to their Billy one.

Distressed leather desk chair. Fun antique desk set...I was thinking Tiffany :)...I like the juxtaposition of old and new.

I think it depends if you want to keep the sleek look or make it warmer. If you want to make it warmer I would add color. Maybe a nice vase with fresh flowers. Good luck!

Go with a plant in a colorful ceramic planter.

Thanks for the ideas everyone, that's what I was looking for! Belle Chaise, yes, I'd like to make it warmer, but still tasteful. hayleydaniels, I'll definitely look for some colourful ceramic pot or a vase, maybe something like this, only smaller:

That yellow box looks amazing Carolyn, colourful yet very sleek and classy. Thank you for sharing it!