Let's say you want to create an image gallery that will pull in to the gallery a single image from various content types. Some of these other content types include a single image, while others include multiple images. Using views: Under fields, add an image field; you will see that one of the configuration options is "Multiple Field Settings". Under that make sure you check the box for "Display all values in the same row". The last line under this will ask how many items you want to display. Type "1". You can also specify which number to start with if you like. Your image gallery will thereby pull in a single image.