Which webservice to use to recieve a .jpg image on a Sharepoint list

Question

I have a sharepoint picture library with a .jpg in the Name column and the full name in the title column. This is part of an electronic scanned signature. My hope is to query the libaray and copy the image to an infopath form. So that the image becomes part of the form. Which webservice do I need to use to connect with the library? If I use astandard data connection to a sharepoint list, I cannot see the column. A webservice is what I believe will be the way. Some services require an operation - which one, and require parameters - how? I have deatils on how to connect using soap - what operation do I use? Then what paramenters etc. Any examples or help apprecaited