You can import .jpg pictures to any of the lists in an Excel spreadsheet (.xls, .xslx) as an object, which is not exactly jpg to xlsx conversion but achieves the very same thing. Most spreadsheets editors are capable of this, as it is one of the most common features.
Some online converters offer this conversion, but they will basically place a picture in empty spreadsheet in most cases.Open JPG file Open XLSX file
An universal picture and document converter
Google Chrome extension for Google Drive
A web-based OCR conversion and text recovery service
Visual processor used to create high quality presentations, charts and graphs