Image data in HSSF is all present, just not easily accessible from the user model. I've been working on a way to get it out to make things somewhat easier.
Created attachment 19294 [details] Patch for picture extraction
This code looks good, thanks for it. Any chance you could knock up a quick test for it? I guess it just needs to extract a pre-defined image out of a workbook, and check it has the right data in it. That way, we can be sure we don't break the functionality in the future.
I added a testacse (see src\testcases\org\apache\poi\hssf\usermodel\TestHSSFPictureData.java) and appllied the patch. Yegor