Save image using wcf data service in wp7.1

here is good example to capture signature

Silverlight application with Capturing and Saving Signature as BMP[^]

and regarding WCF serverice to save that captured signature in database, you can make WCF service that take base64 string as parameter which is generated from bytes array of generated signature image, you can store that base64 string directly to your database or you can convert it to bytes array and store it to database its depend on you in which format you need to store your image.