how to insert image into word document using java
Take a look at the Apache POI API.
http://dev.plutext.org/trac/docx4j/browser/trunk/docx4j/src/main/java/org/docx4j/samples/AddImage.java
Docmosis can do this also. You place an image in your document as a placeholder to get the size etc as required, then Docmosis will inject the given image at runtime from Java.