The picture filename that Herschel holds for every partnumber doesn't actually have to be a picture.
It can be a Word document, or an Excel spreadsheet, or any type of file your PC can open.
Some users take this idea further, and combine several different files and file types into one PDF file, and then tell Herschel this PDF is the partnumber's picture file. For example, for a finished product you could combine pictures of the item, a spreadsheet containing assembly details, technical drawings and test instructions, all in one PDF. When you double-click the picture thumbnail in Herschel's partnumber enquiry, Herschel opens your PDF viewer and displays the file.
Adobe Acrobat Pro can combine PDF files, but there are many low-cost or free alternatives available - try searching for "merge files into pdf".