1. Ikea sells these Platta's for diying a little deck area. This would be a great upgrade over something concrete and can be taken with you when you leave. It's not too expensive: each 17" x17" square is $5.99.
2. Flor sells all kinds of modular carpet tiles and some are good for a covered patio or balcony that isn't going to get soaking wet. They have a version of astroturf that could be really fun, or you could try Home Depot for the real thing.
3. If your deck is already painted, you can stencil it (the image is from Holly's Hip Stencils) or paint it another color since you can always paint it back before you move. If your deck it tiny it won't be too labor intensive. Don't forget to try out some eco friendly exterior paint.
4. Recycled plastic rugs are another great, durable solution for the outdoors. We've had our eye on this one from Viva Terra for longer than we can remember. The soft hues along with the fact that we can take it with us wherever we go. For $50 it seems worth it, as long as it's as durable as they say.