I assume because you used the word presentation that you will be in Slide Show mode at the time you click the picture. This presents a bit of a problem for a macro to open an Excel spreadsheet because when PowerPoint is in Slide Show mode I do not believe it will yield the screen to other applications. So your code has to open the Excel document and then exit Slide Show mode, in which case it would leave you in the awkward situation of having to manually re-start Slide Show mode to continue the presentation.
I would recommend instead that you copy and paste the Excel spreadsheet of interest into PowerPoint (could be on a hidden slide) as an OLE object, then tie this object or slide to the image (button) of interest so that you could go directly to the spreadsheet without leaving Slide Show mode.
I hope this helps.