This is very much possible.
Go into the Edit mode of a tour and you will see all spots on the right. Hover over a spot to see the options.
Click the download button as indicated on the image below. This will open a new tab and by right clicking and selecting Save as, you can save the picture to your computer.
When you're done editing the pictures, you can reupload them using the upload button as indicated on the picture below. Careful: this will override the old picture.