There is a lot of different gallerys in Second life. Very big ones with many paintings and some good art. And the small ones often run by the artist with a few pictures or sculptures.

In the big ones you get a big dose of all the culture you could want.

 

Crossworlds gallery

http://maps.secondlife.com/secondlife/lynto%20land/128/128/89

But I rally prefer walking around in a city block finding small gallerys and designers or maybe a strange store or two.

Virtual soho

http://maps.secondlife.com/secondlife/Bembecia/177/174/104