We have released a new plugin, Simple Matted Thumbnails. This provides a new format for thumbnails in addition to the two that come with WordPress.
This is a choice available from the media settings for the thumbnails and in the settings of many e-commerce plugins. The image is cropped to the exact size requested, care must be taken in preparing images to avoid losing important content.
This is the new format provided by this plugin. The image is resized proportionally to fit in the box and then matted out to the size requested for the thumbnail. The mat is similar to those used to frame photographs and watercolours. This plugin lets you choose the colour of the mat and add extra matting around the thumbnail image.
Matted with extra matting
Where to Get The Plugin
The plugin is available from the WordPress Plugin Repository at http://wordpress.org/plugins/simple-matted-thumbnails/ and using the Plugins menu in the WordPress admin. Please let me know of any issues using this plugin and any enhancements that you would like to see.