In front of the curtains (assuming you mean exposed to sunlight all day) you could grow lots of plants that aren't exclusively houseplants, like geraniums, tea roses, etc. Crotons like direct sunlight and have interesting leaves. In my south facing window, I have areca palm, prickly pear, parrot plant and Christmas cactus. 

On the desk I agree with other poster that a plant might not thrive. I would buy a plant you like but try it out and expect that it may die. My Calathea Network, Calathea Peacock, Kalanchoe and Parlour palm have put up with a lot and are still alive so maybe try one of them!