sjarrel's suggestion is a good idea. Having stuff on a flashdrive (usb memory key) makes it transportable among devices and easy to maintain and access.

For now, you can move your content out of the Library and into the regular file system as follows:
- tap "Library" on the home screen
- tap "Images"
- tap the checkmark at the top right corner
- tap each image so that it shows a checkmark in its top right corner
- tap "Export" at the bottom of the screen
- tap "Internal Storage" (not the "Select" button)
- tap the "Select" button beside "documents" in the list of folders

This will copy the selected images to the "documents" folder. You should then reselect them in Library and this time tap "Delete" at the bottom of the screen to free up the space in your Library.

The images should now show up in Gallery, although it may take a few minutes for the Gallery to find and index the images.