Consider your space, is your office or living room minimalist and modern, or in a more transitional design style? If it's more traditional, go for a classical print or maybe a small more landscape. If your space is modern, perhaps opt for an abstract or bold colourful line art piece.
Do you want this piece to be the focal point of your shelf, or is it meant to be more subtle and blend into the shelf? Neutral pieces are always a safe bet to style on a shelf, but consider playing around with a fun pop of colour.
If the art piece is being styled on a shelf, keep it smaller, perhaps an 8x10 or a 10x13 framed art print. These look great on modern shelves and won't look out of place or too big.
The frame should be a simple frame, a neutral wood or black frame is a perfect choice to style on a shelf. These simple thinner wood framed art prints are a classic style.
Lastly, how do you style the shelf around your new art piece? Remebr to stagger the heights of the objects on the shelf. Add a few taller objects such as candle sticks, vases or books, and some smaller pieces like wooden bowls or small pottery.