good work
first design : i think you should make it more darker , text is bad , try to add some effects on the image not only fractical
second design : it's good but you adding more light, make it darker
third design :i think it's not good, you should add some effects on the fractical to make it fit with the design , the text is too bad too
, try to add something like (bevel & extrude ) or something like that to make it better >>"D
forth design :effect is good , background looks bad, text is perfect but you need to decrease the opacity of the grunge texture ^^
anyway it's a good start, and practicing will make you better
good luck