Hi Srikanth,
Each DM account has a configuration setting called "Reply Image Size Limit." It specifies the maximum reply image width and height that can be returned to the client. The server returns the "illegal image size" message if a request would cause a reply image whose width or height is larger than this setting.
To adjust the MaxPix, log in to DM cloud(Scene7 Publishing System), and choose Setup > Application Setup > Publish Setup > Image Server > Reply Image Size Limit. Increase this setting to a value you think is sufficient, and save it. The current limit is 5000 x 5000 pixels. The Dynamic Media servers currently don't serve up images that are larger than 25 million pixels.
Thanks