New version of Simple Snowfall Effect is major update that brings many new features: set direction to up instead of down, control opacity for flakes, select multiple images for flakes and set rotation for them. And get preview on admin side too.
Plugin 2.0 version is a major improvement over previous one. You can change direction to up, so you can use balloons or something else instead of snow, getting the float / rise effect. Also, balloon and hearts images are included with the plugin now. Check out developers guide to get info on how to include your own images too.