Thank you Sergey for setting me right!
But what should I put in the params? In general how can I figure out what the param value needs to be? The scriptaculous documentation you had shared in your posting, doesn't describe the param names needed for richfaces.
I tried <rich:effect type="scale" param="originalHeight:200,originalWidth:200,scaleMode:box"/> but no cigar.
Thanks in advance.
rich:effect is a wrapper for scriptaculous effect set. Try to make a working test example outside of richfaces and jsf. Just picture, prototype.js and scriptaculous.