if you provide some reference to what your critiques are like, would be helpful for people to see if your opinion is valuable. personally, I prefer the critique of professional art directors and artists myself, someone with a resume. Actually, that person is my uncle, who worked as an art director for a major publication for 20+ years. you have to understand, that not everyone is going to like critique, and its good to couch critique in a way that you are giving pointers to improve the work, not tear it down. The objective is to produce a better piece of artwork, so think of yourself as a teacher, not a critic. Also it helps to understand the media you're critiquing, because if you don't understand it, you may not know what its limitations are, and not be able to give appropriate pointers in how to improve as a result.