If the poly planes are for Image references then insure you have the poly plane set to the same size as the original image, change Mayas default geometry measurements to cm's and check the image to ensure they match.
If its just to map a file texture then please ensure you UV Map it correctly. There are free tutes here that cover UV Mapping and also in the Maya Help Files (F1) and there are numerous tutorials online that cover creating image planes.
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