[Misc] Update Default Image Mapper Error Log (#8977)

Signed-off-by: Alex-Brooks <Alex.Brooks@ibm.com>
Co-authored-by: Roger Wang <136131678+ywang96@users.noreply.github.com>

vllm/multimodal/image.py

@@ -56,7 +56,12 @@ class ImagePlugin(MultiModalPlugin):
                     .preprocess(data, return_tensors="pt") \
                     .data
             except Exception:
-                logger.error("Failed to process image (%s)", data)
+                logger.error(
+                    "Failed to process image (%s) with the default mapper. "
+                    "This is most likely an edge-case with this model's image "
+                    "processor in transformers (type: %s), and not vLLM.",
+                    data,
+                    type(image_processor).__name__)
                 raise
 
             return MultiModalInputs(batch_data)