I'm new to blender and completed my learning section, and now I play around with blender mostly rendering objects/scenes. Can I upload my rendered images here for asking critiques?
If answer is "No", is there any other SE site for this?
The answer is "No." That type of question is off topic and would be closed as such.
Point six on our off topic list, "Critique and Showcasing."
If you think of BSE as a collective resource that will help future users, a question like "what do you think of my render?" probably will not be useful for anyone but you who made the render. That is part of the reason for having them be off topic.