You can make a fantastic display with African Cichlids. The general rule here is to keep them crowded as this dilutes the agression. Because of this, you will need to think about some serious filtration, i've kept them with 2 large Eheim cannister filters on the tank and it worked very well. These are hard water fish, and will appreciate the addition of a decent alkaline buffer for the water - your dealer will be able to help you with this. For aquascaping the tank, you MUST use rock that you buy from your local tropical fish store. I wouldn't trust anything you find at the beach, in your garden etc, it's just too risky. So called 'Ocean rock' - available from your dealer, is very good for these fish but see what they have available. Remember to put the rock in the tank before you add any sand or gravel - this will give you a more stable structure and reduce the chance of rockfalls when the fish start digging. They're not difficult to keep, give them plenty of cover to chose and establish territories and they will be fine. As for how to aquascape, it's a matter of personal taste, but try to consider the fishes requirements as well as what's asthetically pleasing. If you find there's a little too much agression, it may be because there are not enough areas in the tank for the fish to use as territories. Try to create as many caves etc as possible so they have a wide choice. Generally, keep larger heavier rocks at the bottom of the tank, and build up outcrops, caves and overhangs from there.
Hope this helps you,