Another subtle update to the Gallery feature has been pushed out. This update brings to the Edit Gallery screen the ability to select image size, which was previously available only by directly editing the Gallery shortcode in the Text tab of the Post or Page Editor.
When you open the Media Manager’s Edit Gallery screen, beyond Link to, Columns, Random Order and Type, you’ll now see an additional drop down menu which allows you to select Gallery image size- Thumbnail, Medium, Large or Full Size. While I have not had an opportunity to experiment with all the Gallery Types, in the past these image size choices have been relevant only for the default Thumbnail Gallery and not the “mosaic” type of Gallery.
Your image size selection should also influence the number of columns you select to use. If your theme has a particularly narrow posting column or even a full-page template, you may need to experiment a bit with image size and number of columns to get the best result for your theme.
And here’s the bonus: you can now easily insert even a single image which will be displayed in a Gallery and then, by default, the Photo Carousel. If you wish to align your single image to the left or right and have text wrap around it, you’ll still have to get your feet wet in the Text tab of the Editor, but it’s a grand start!