Apparently not - as I took this photo of the door to Hieronymus' shop just the other day. It's definitely him: he's probably painting more bizarre mouse/giant strawberry/scary bird/naked humans paintings right at this very moment.
Hieronymus Bosch lived from around 1450 to 1516, and was born in a town called s'-Hertogenbosch, about 80 km south of Amsterdam. I kid you not. The s' is part of the name. It gets even better: in 2004 s'-Hertogenbosch was awarded the title of the European Fortress City of the Year.
Not much is known about Bosch. I feel that, judging from his paintings, that he was clearly crazy. Either way, his work is highly symbolic and utilizes a dense system of iconography. Some view his work as a super-proto-type of the surrealist work of people like Salvador Dali, but others view it as visual translations of Medieval biblical and folkloric tales.
It is uncertain how many paintings by Bosch survive: he only signed seven. The generally accepted number of works is twenty-five, many of which are in the Prado in Madrid (Philip II of Spain, 1527-1598, really liked his work). There could be any number of paintings by Hieronymus Bosch though, especially if he is still active, working in Amsterdam these days.
These images, what I think of as some of The Ultimate Hieronymus Bosch, are from the 1503/1504 triptych, The Garden of Earthly Delights.
Every time I look at this one, I think, "What is going on, Hieronymus?"