What the Transparency Cydia tweak does is allows you to customize different aspects of your app icons. You can for example make your app icons transparent, get rid of the shadows or badges, remove the date on the calendar app and so much more!

It's a prety good tweak for me, and if you wanna do customisations without that memory hog, Winterboard then i recommend this.

You can get it for free from BigBoss repo.