Do you think, data validation feature allows you text selection only? Let me convince you are mistaken. You can donwnload the Excel file with live example extending data validation ability to work with embedded images list.
The images aren’t in the dropdown (that’s what I thought), but the validation selection changes an adjacent image. The workbook has very detailed instructions for how to do it. Even if you have no use for it, there are cool fish pictures to look at.
The author, Jiri Cihar, writes:
Entirely free of VBA.
You’ll get a macro warning dialog because there’s an empty module in the workbook.