1. Know your genre. Different criteria are set for different genres. For instance, a stylized animation character design or concept arts might not need to look ultra-realistic, but environment designs and others do. 

How do you know that your work fits as a top-notch work for a specific genre? Please, look at the render and ask yourself: 'If I'm looking for the best artist for this specific task, would I hire this artist?'

2. If your render is an Arch Viz or a Product Viz, it needs to be more than realistic. Such renders are now a dime a dozen. (Moreover, modelling an imaginary interior room or things does not mean it's an arch viz or a product viz. Such criteria falls into 3D visual representation of buildings or products that have been carefully designed by engineers or craftsmen. Otherwise, your render will fall into the category of concept arts or environment designs.)

3. A Fan Art is a most unlikely candidate for this award, unless it obviously excell the original art to a considerable degree (which is very difficult to achieve).

4. Have your online portfolio--or other works--available to demonstrate that some flaws (such as "unrefined textures or modelling") shown in your renders are not an evidence of your lack of competence. 

Final Image: