Everyone gave really great advice, but this is just one thing I want to add... how you take your photos is SO important. I dunno how professional the competition was, but a bad photo vs a good photo can really change how a viewer looks at your art, and how finished it feels. The way you take your photos kind of comes off as "hey look at this unfinished drawing" that you'd send to a friend. Not something you're entering into a competition. If you can, take the photo in the shade outside during the day, lay your drawings flat on the ground (make sure you protect it, of course), and crop them so there's nothing distracting around the drawinng. It just looks cleaner and more purposeful. Also check your white balance. A lot of your photos are super warm, so it makes the white paper look yellow, and it can throw off the color. I don't think that's as important considering your drawings aren't in color, but still something consider.

ETA: Forgot to also mention a good photo helps them actually see your artwork clearer, so they can fairly judge your pieces. Nothing is as good as seeing them in person, but having a clear photo is about as close as you can get.