A WordPress plugin that lets you create rows of images easily within your content with one simple shortcode.
Yes this plugin should be compatible with all themes. The row of images will be 100% width of the content area it is included in, and within that images should all be equal widths and equally spaced.
The images displayed will be resized to be 1/X the width of the image row, where X is the total number of images. If there are three images in the row, the image will be 1/3 the width of the row. This means size is not as relevant in this situation, your main concern will be with with the aspect ratio. If your images are all the same ratio you will not have a problem, but if images have different heights at the same width this plugin will not attempt to fix that and you will just have images that are not the same size.