First, open your game and take a screenshot that clearly shows the main gameplay. Try to capture the most important character, vehicle, weapon, enemy, ball, or object used in the game.

Do not worry if the objects look a little small in the screenshot. The screenshot will be used as a reference so the AI understands the real game style and models.

Then upload the screenshot to an AI image tool such as ChatGPT image generation and use a prompt like this:

Create a promotional game thumbnail using this gameplay screenshot as the reference. Keep the same characters, vehicles, objects, colors, and visual style from the original game. Make the main game elements much larger and closer to the camera so they are clearly visible even at small thumbnail size. Remove unnecessary UI, buttons, debug elements, browser borders, and empty space. Improve lighting, contrast, sharpness, and composition, but do not invent characters or gameplay elements that are not present in the screenshot. Make it look like a professional mobile game promotional image. Final format: 512x384 pixels, 4:3 aspect ratio, no text unless text already belongs to the game.

For best results, developers should take a screenshot where the important objects are already visible. AI can improve the composition and zoom, but it works much better when the original screenshot clearly shows the actual game models.

A simple workflow is:

1. Run the game.
2. Take a clean gameplay screenshot.
3. Upload the screenshot to the AI.
4. Use the prompt above.
5. Check that the generated image still represents the real game.
6. Export or resize the final image to 512×384 pixels.

The most important rule is: use your real game screenshot as the reference. Do not ask AI to invent a completely different promotional image.

Where to put your example images

Under “How to Make the Thumbnail With AI”, use this order:

Step 1 — Take a Screenshot From Your Game

Upload the original screenshot directly from the game here.

Caption:
Original gameplay screenshot — use this image as the AI reference.

Then explain:

Open your game and take a screenshot showing the main characters, objects, vehicles, weapons, or gameplay mechanic. The important game models should be visible because the AI will use this screenshot as its reference.

Step 2 — Upload the Screenshot to AI

Then show the prompt:

AI Prompt:
Use my uploaded game screenshot as the reference. Create a professional Play Store/game thumbnail using the same characters, objects, models, colors, and game style. Make the important game objects much larger and closer to the camera so they are easy to recognize at thumbnail size. Improve the composition, lighting, contrast, and visual quality. Remove game UI, buttons, debug controls, browser elements, and unnecessary empty areas. Do not invent characters, vehicles, weapons, or gameplay that are not present in my screenshot. Keep the image representative of the real game. Final image must be 512×384 pixels (4:3) and contain no added text.

Step 3 — Show the Result

Immediately after the prompt, upload the improved image I made from your screenshot.

Caption:
Final promotional thumbnail — created from the original game screenshot.

Original Game Screenshot → Upload to AI + Prompt → Final 512×384 Thumbnail

For your cannon example, I would put the small original gameplay screenshot first, then the improved image with the large cannon and large balls directly underneath it. This makes the difference very obvious.

If possible, on GameMonetize I would actually show the Before and After images side-by-side because developers will understand the tutorial much faster.