What makes a good stone?

Boy, am I sorry I found THIS site! I had no idea about Suiseki, yet I have quickly found another passion! I have a knack for finding great stones and a keen eye for artistic detail. Is there a size limit on the stones? I have a water-polished piece of Serpentine, a smooth twin-mound stone about 50-60 lbs. with a flat bottom. It has always been a favorite stone, with a powerful presence, and a fabulous green mottled color when wet. It reminds me of two steep treeless hills.
Now I want to build a rustic holder for it, since it will have to be outside, in a manner like I've seen on the stones represented on this forum, but not so finished and polished.

Geodude: What I wouldn't give to have you peruse my collection! I know what most of my rocks are, but some IDs elude me. We live on the convergence of four mountain ranges of different composition, including volcanic, wonderful rock hunting!

Just what I needed, another hobby! Hmm-m lets see, koi, ponding, bonsai, gardening, carving, etc. etc.