Is it possible to search uploaded images, for example type 'pie chart' and see the images connected to those posts?
For SE's own tools, no, it's not really possible since images are stored just as that, image files. There's no metadata that describes if an image is a pie chart or anything else.
If users properly describe the alternative text on image markdown as "pie chart", e.g.
![example of pie chart](https://i.stack.imgur.com/i0ey1.jpg)
then it's possible to search for that using SEDE (as of writing, there's none). However, SEDE is updated each week.