To upload screenshots, without making albums, simply register on imageshack.com and upload them there. then copy the "direct link" and paste it in the code .
If you want otherways create an album or post a comment to your map, clicking "go advanced" and uploading the screenshots there.
Remember: always save the screenshots and pictures in .JPEG (.JPG) format to upload them!
Hope that helped you to upload screenshots to your map :)