Add lots and lots of grit to help drainage and keep the soil poor. Different levels make for more interest and you can add large rocks/stones or pieces of slate, looks better if 1/2 buried and the grain of the rock going the same way. Miniature firs can look nice and add interest but make sure they are the ones that only grow 1" a year. When choosing the plants some can be very invasive and take over and some can be extremely slow growing. MIniature bulbs can also give interest.
After you have planted up put pea gravel around each plant to protect the growth or cover the bare ground with coloured - chips gravel, or slate, Look at the Goypeadia pages on Alpines, Rockery ideas and Phlox for lots of ideas