[Doc] complete the clarification on batch image generation (#567)

Signed-off-by: Huang, Zeyu <11222265+fhfuih@users.noreply.github.com>

docs/user_guide/examples/offline_inference/text_to_image.md

@@ -23,6 +23,23 @@ if __name__ == "__main__":
     images[0].save("coffee.png")
 ```
 
+Or put more than one prompt in a request, processing them sequentially.
+
+```python
+from vllm_omni.entrypoints.omni import Omni
+
+if __name__ == "__main__":
+    omni = Omni(model="Qwen/Qwen-Image")
+    prompts = [
+      "a cup of coffee on a table",
+      "a toy dinosaur on a sandy beach",
+      "a fox waking up in bed and yawning",
+    ]
+    outputs = omni.generate(prompts)
+    for i, output in enumerate(outputs):
+      image = output.request_output[0]["images"][0].save(f"{i}.jpg")
+```
+
 ## Local CLI Usage
 
 ```bash