One great masking effect that doesn't use masking which I love: If you have a tall-ish avatar with a transparent background, overlay it on a coloured circular

One great masking effect that doesn't use masking which I love: If you have a tall-ish avatar with a transparent background, overlay it on a coloured circular div (border-radius: 999px) and set only the bottom corner-radius. That way it sticks out the top, which looks great and only a few lines of CSS.