All images, that user upload have different proportions and sizes and after resize this fact stays that way. When placed together such images don't look very symmetric. I propose to add new "fill" option to image helper, that will allow to specify color, that will fill margins left after image resizing, so all images will be the same size, but will different margins.
Usage:
1. catalog items/categories:
<inp2:prefix_Image render_as="article_image" thumbnail="1" DefaultImage="img/no_article_image.gif" Fill="#FFFFFF" MaxWidth="143" MaxHeight="124" DefaultWidth="143" />
2. other items:
<inp2:prefix_Field name="ImageField" format="resize:100x200;fill:#FFDD00"/>