Have you ever adopted a magazine theme with a grid layout only to realize your small images don’t get upscaled, leading your grid to look funky? The Thumbnail Upscale for WordPress could help you fix that issue. The plugin upscales small images to the specified thumbnail dimensions as long as you have the crop setting enabled.
Thumbnail Upscale is not perfect, but it can help make your grids look less funny when you have images with different sizes. This is a free plugin.