Attaching driftwood to suction cups allows you to create some very neat, and realistic looking, aquascapes. I prefer to use plastic screws (regular screws made out of very hard plastic), but they can be hard to find. The second choice is aluminum screws. Ask at your local hardware store for some type of screw that will not rust. I am sure there are other options. The suction cups I use are sold in aquarium shops as heater/ airline holder suction cups. They are cheap (US $1.99 for six last time I bought them). I am sure that there are other sources for these also.

As for designs... I have used gnarled branches just stuck to the back of the tank all over (similar to using silicone to attach slate). Fill in the gaps with lots of Java moss and Anubias spp. This gives a nice background. For 3-D set ups there are two options. One is to collect straight and forked driftwood. Stick the top to the back of the tank and the bottom to the tanks bottom. This gives a 3-D effect that the "roots" are growing from the back of the tank and into the tanks substrate. It looks very natural and provides a great maze for the fishes to swim through. The other option is for a SE Asian tank. Replace the driftwood with bamboo and plant hygro, crypts, etc for a nice Asian bamboo swamp.

I am sure that others have other ideas about how to attach the wood. These are just three set ups that I have really liked.