If the closest you’ve come to attending an art show is buying a $17 sofa-size painting at a Starving Artist show, get a culture shock on Saturday at the Gateway Arts District Studio Tour. More than 30 painters, mixed-media artists, sculptors and photographers will open their studios as part of Mount Rainier Day in Prince George’s County. The event will include the work of artists living at the Mount Rainier Artists’ Lofts, including Joel Traylor,…