Does a Romanian omletă ţărănească (peasant omelette) have standard ingredients?
Judging from search results and the handy firefox babelfish addon, the peasant (or country-style) omelette seems to be, as you suspected, one of those dishes where anything handy is thrown in. 

EDIT: the firefox addon is actually unnecessary as google provides an option on the search results page for translated versions of the search results.