I want to new custom option as a image. while adding a product i need to add a custom image option filed.
I think what you are describing is swatches. Which you can only use in Configurable products at the moment. Maybe depending on your product type this might be a better method to use?
Alternatively, if you are set on using custom options and if you don't want to build in the module yourself you can choose one from the marketplace:
Change the custom option's input type to file. Please check the screenshot
For Image in attribute
Goto Catalog->attributes->Manage attribute->add new attribute. Give all details... For "Catalog Input Type for Store Owner " select Media image and save it.
Then goto manage attribute sets.. Select your attribute set. For Example, select Default. Then drag and drop your attribute in that. Save it. Goto product creation page. You will find the image option.