Souzai are a type of pixel emoji/emoticon, often used on blogs to express emotions. They are larger than typical emoji and are very similar to 'doll' graphics. They come either with or without text, however the text is almost always in japanese.
Gyaru culture has its own set of souzai, featuring gyaru style girls expressing various emotions and saying different things. These souzai are very popular additions to gyaru blogs although they are seen less frequently now than they did during the early 2000s. Gyaru Souzai are more commonly reffered to as 'Gyaru Pixels'