lib/core/template.js
function (image) {
      const imageName = path.join('images', image)
      const thumbName = path.join('images', `${image}.thumb.jpg`)

      const thumbPath = path.join(destination, thumbName)

      if (fs.existsSync(thumbPath)) return thumbName

      return imageName
    }
function (image) {
      const imageName = path.join('images', image)
      const thumbName = path.join('images', `${image}.thumb.jpg`)

      const thumbPath = path.join(destination, thumbName)

      if (fs.existsSync(thumbPath)) return thumbName

      return imageName
    }
If a thumbnail exists, return it. Otherwise, return the base image.