While it has always been possible to add images to the canvas of your Google Docs spreadsheets, you can now insert images inside individual cells as well.
To add an image to a cell, highlight the cell, click F2 to enter the formula mode and then type =image(“URL”) where URL is the public web address of that image.
Google Docs, by default, will scale the image to fit inside the area of the selected cell but you may change the default settings by adding another parameter to the image function.
For instance, a formula like =image(“URL”, 2) will stretch the image to fit inside the selected cell while =image(“URL”, 3) will insert the image into the cell at its original size.
Refer to the documentation for more details.