Delete image files embedded in excel

Hi guys,

I'm trying to upload an .xls file to this forum but it is too big. I know that I used some pictures that were serving as backgrounds for bubble graph within that file. How can I delete pictures embedded in Excel ?

File is over 3MB, and even if I delete the chart which contained those pictures I still have pretty much the same size. How do I get of that junk inside spreadsheet ?

Thanks!
vemix