From VOA (link):
Huang Rui, an artist and one of the organizers of the festival, says certain themes are off limits.
“Some officials don’t like artworks with themes of leaders since Mao, or thoughts of the leaders, or the Tiananmen Incident,” Huang says. “These, for them, are very sensitive. In fact, these factors are like a spring. If there is any restriction, it is actually an incentive for artists to create.”
“You see a lot of artists who just want attention, who use the very obvious routes, and of course that’s the easiest thing for the government to respond to,” she says. “But, if you want to find real quality, real powerful art there’s some great statements being made. And those artists, really I don’t think they’re being constrained in any way from saying what they want to say.”