Pictures need to be less than 1MB for you to be able to add them to posts. Lowering the window size of the game helps you take smaller full screenshots. You can also try saving the screenshot as different filetypes before copying it over. I forget which format works best. Maybe JPEG?
If you are unable to upload the images, either convert them to JPG format, or upload to image platforms such as imgur or postimages and link them in the report
