These are context-free grammars with regulated rewriting: each production is context-free, but its application is regulated - permitted or forbidden - by context randomly distributed in the developing picture. Random context picture grammars (rcpgs) generate pictures through successive refinement. For each class we develop a necessary condition, in particular, a pumping or shrinking lemma, and show that it is properly contained in the class of rcpgs. We show that these grammars are more powerful than... We also introduce a broader model, so-called generalized random context picture grammars. We investigate three important subclasses of rcpgs, namely those that use no context, only permitting or only forbidding context. The terminals of such a grammar are subsets of the plane, while the replacement of a variable involves the building of functions that will eventually be applied to the terminals. Syntactic methods of picture generation have become established during the last decades.