MindMup now makes it easier to improve your map visuals by copying and pasting images directly into a map. Previously, you had to upload an external image file or drag it onto the map, but now you can easily just copy and paste images in all the recent browsers. This allows you to copy/paste parts of images, and pull in screenshots.
To use the new feature, just copy an image using your standard OS clipboard features, and then paste it into the browser window using the browser Edit menu, or the standard keyboard clipboard shortcuts (Ctrl+V on Windows/Linux, or Cmd+V on a Mac).