Are you also wanting to hide the Slide to Unlock text? The theme attached below will get rid of the slider and the slider background. (It also gets rid of the clock background; if you want to keep that, delete the BarLCD files from the theme.)
Pretty sure you can find all these tweaks in Cydia, though. For instance there is an Invisible Tap to Unlock available. Poke around and you'll find something that works!
edit: I forgot that I left some padlock sliders in there...just open them in an image editor and make them transparent and they'll be fine.