Are the images inserted as image or as a base64 string?
In the first case; no clue how to approach this, as images inserted in an excel aren't linked to a particular cell.
Second case: you can use Base64DecodeToFile of the Community commons module
Excel reading is done via the Apache POI java library. Both the default Mendix functionality as well as Excel Exporter module use this library.
Probably easiest to create a separate java action to read this from the imported Excel. See an example code snippet and especially the answer from Apache POI guru Axel Richter.