Not from a screen shot, no. Typically I have found mystery galleries to be added by shady apps like the crappy stupid games my kids install on our tablets. A lot of these devs don't follow protocol and game images, videos, etc seem to end up in gallery. Similarly, a lot of the ads that appear on these games tend to store images and video clips on the device as well and show up with weird folder names. All you can do is see what the contents of these folders are and identify where they are coming from. You can use a file manager like estrongs to look through the SDcard and also delete the offending files.