My idea of a contemporary yard is a very angular layout (ie no curves). As for plants, bamboo (need to install with barriers), slender papyrus, sculptural succulents in square pots (like aloe or agaves). Grasses like dwarf blue fescue in repeated patterns.

In terms of colors, no riot of colors. Just a couple. I do not think that black is a must for the contemporary effect; however avoid tropicals since they evoke very, well, tropical images.

Minimal use of structures and a plain concrete patio, to achieve a minimalistic effect.

Just my 2c.

I think if you better define what you mean by "contemporary" it would help. After all, Home Depot is full of "contemporary" plants for the soft-scape and contemporary building materials for the hard-scape but I don't think that's what you are looking for.

Current trends seem to be going to drought tolerant plantings, xeriscape plantings and native plantings....

You might want to look at the gardens of landscape architect Isabelle Greene for inspiration.

Here is a link that might be useful: one of her garden designs

I saw a very modern-looking garden that was a simple grid of mexican feather grass, Stipa tenuissima. Might have been a very tall cactus or dracaena as well, don't remember...

I'd suggest watching some of the landscaping shows on HGTV and diynetwork, if you get those channels. A few that come to mind are "Garden Police," "Desperate Landscapes," "Landscapers' Challenge," "Yard Crashers" and "Landscape Smart." Aside from that, all I can say is that minimalist design is supposed to be the trend du jour.

Just make sure to buy your plants through the year so you have interst in all the months. A contemporary garden does not have to be static and unchanging. Look for plants that change color in the seasons or have interesting seed heads. I think a strong water feature is one of the best investments you can make. One of my friends from work just repainted his garden walls from golden-red to blue-turquoise! Looks like a whole new garden! Next year he's going to paint another color. Good luck with your design.

Specimen succulents in a grounding of DG. Phorminum. In other words, plants with bold architectural shapes. This would also include clipped hedges and "cloud pruned" shrubs and small trees. Color through foliage, not flowers. Negative (empty) space is important. Gravel. Stone.

The horsetail would have worked in heavy containers without drain holes for the roots to escape out of. It is a plant that must be carefully contained.

Stipa tenuissima, mexican feather grass, though it is extremely beautiful, is agressively invasive, so I wouldn't suggest that.

I saw a photo of a church in San Luis Potosi, Mexico, where they planted phormiums in rows that all lead to the front door. Try to immagine the door as being a focal point and the rows all came out from the focal point in an array that resembled sun rays. If you want really sculptural plants, you could try agave desmettiana varegata, or agave attenuata, both of which are user-friendly agaves and provide sculptural impact. Agave Desmettiana variegata stays to about three feet in diameter and thee feet tall. Agave Americana Medio-Picta Alba is another agave that comes to mind, although that one does have sharp spines. Strelitzia Juncea, like you already mentioned is a good plant for your purpose.

I would stay away from grasses that grow tall and untidy. They can completely defeat your purpose of contemporary. The dwarf fescue grass, like someone suggested is good because it is rigid, not tall and wavy.

Although most tropical plants evoke a jungle look, some can actually be very sculptural. If you have the space, a Phoenix Canariensis, or Dactylifera could serve your purpose. It could be a focal point and also serve as a vertical component to your yard, since a traditional tree would also take away from the formal, contemporary look. Others that come to mind are draceana draco, Yucca Guatemalensis, Cordyline Australis "red star", Dypsis Decipiens, Bismarckia Nobilis. These last three provide color throught their foliage, and the bismarckia, especially, gives great contrast to green foliage. Dypsis Decipiens has reds, yellows and oranges in the emerging fronds and the upper portion of the trunk. The phoenix species provide color when they drape themselves with bright yellow-orange inflorescents, then followed by large clusters of fruit (if the palm is female). If you could find a phoenix rupicola, they have red fruit instead of yellow, and they really stand out.