I'm looking for a word for an artwork that was made exclusively to express an idea of the artist without him or her trying to tailor it to a specific audience.
The word abstract comes close because abstract paintings are usually not made for a specific client, but a painting of a landscape could also fit the description above.
Another word I've considered is un-commissioned art. This word comes very close, but the meaning seems more like no-one paid for this rather than it was an original idea by the artist.
The Dutch sentence I'm translating from is Vrij werk which literally translates to Free work. In English this would be interpreted as art one doesn't have to pay for (free) which isn't the meaning I'm looking for either.
Example sentence: ARTIST is famous for his WORD paintings, which only became highly appreciated and valued after his death. During his life ARTIST made both WORD and NOT-WORD paintings, but his only income came from the NOT-WORD art he occasionally made for noblemen.