Such a place does exist actually, it's called the Groening Fanworks Central (formely The Simpsons Fanworks Central) and specialises in people posting fan art and fics for both Groening shows to be commented, either final versions or draft ones so that you can get help and advice. Though the amount of people actually commenting there lately has been rather low actually, which is kind of sad. Still... you're bound to get at least a couple of helpful comments, and it certainly won't hurt to give it a try. The URl is... http://www.simpworks.com
Just go to the forum section, sign up to it and you're away. The advice is friendly and helpful when it comes, and you certainly won't get flamed. And we do need more contributors there overall.