Running top to bottom, here are the ones that will likely need a replacement or tweak.
Tiny Dangerous Dungeons - The game is beautiful, but something about this shot doesn't work for me, and I can't put my finger on what.
Greenie - Need a cropped shot.
Mr. and Mrs Tart - Need proper aspect ratio.
Lumber John - Need a cropped shot.
Catventures - Need a cropped shot.
Infinite Dungeon - Need a cropped shot.
Minefall - Need a cropped shot.
Monkey Monster - Need a cropped gameplay shot or logo in the proper aspect ratio.
Kids Learn Animals - Need logo in the proper aspect ratio.
Baita Balao - Need a cropped shot.
Eye Copter - Need a cropped shot.
Oh No Goblins - Need a cropped shot.
Swinger - Update your Stencyl Arcade entry with a logo.
World Chaser - Need a cropped shot.
Escalate - Need a cropped shot.
Run Pixel Run - Update your Stencyl Arcade entry with a logo.
Neon Cat - Doesn't look good on a white background. Replace with a gameplay-based shot.
THE CUBE - Low contrast, looks bad on white.
Little Big Cube - Need a cropped shot.
REMUVER - Need a cropped shot.
Gem Bomber - Need a cropped shot.