If you're looking for "general art", you're dealing with an incredibly tough subject, because each specific field of art requires just as much focus as the field of computer programming. There are few similarities in technique between composing and popular songwriting and rap, for instance, in the field of music alone. Oil painting and photography and sculpting and weaving are all drastically different. So the only depth you could get on a general art site would be something like "Look at such-and-such pretty thing," unless it was very cleverly designed to allow for more in-depth conversation. Then you'd have to convince those sorts of people to use the site, and some varieties of artists almost routinely avoid the Internet.
Hacker News works because programming is very online-intensive as-is. Art isn't. Making the transition is very hard. I should know: I've made three attempts thus far.