Pdfcrowd is a web service and all conversions run on our servers. So all assets must be accessible remotely. Your background image is using link to your local PC (C:\CMS\Executable\recurs\image1.png), we can't access it.
You should either add your image to some public server or use convertFile, convertFileToFile or convertFileToStream method and add all assets into a zip file.
https://pdfcrowd.com/api/html-to-pdf-java/#convert_file