Wow, you're pretty good at this :3 I really like the Greenday one. You know that they're coming to Aust. in December? xD I have no complaints on that one. The Vivi one, I think is great. Personally I hate borders. Maybe reduce the glow on it, other than that I like it. It's adorable >:3 I know you love purple and the third one is great. I just would'nt have that spray effect on the squares, but on the last image it looks alright. You've done a great job, so keep up the good work :3 ~Cleo.
The backgrounds of the first, second and third are the exact same thing but with different colors, and the forth tag in general is just a blending of the first three. Not to mention that you seem to have used the same brush set for all of them. =/ You need to be able to make your tags distinguishable, but all four of these are essentially the same tag with different color schemes and stocks. Also, 99.9% of the time, the dissolve blending option looks pretty bad. I'd avoid it in general. Look up a smudge tutorial, download some new brushes from deviantART, and make some more unique tags. You'll get there.
For the first one I like the greenish glow on the Vivi text, that's nice. I like how you made him pop off a bit from the edge. The only thing you should work on is adding a light source in there somewhere because the lighting looks a little bland at the moment. As for The second, third, and fourth one the smaller text is a bit hard to read. On the Green Day on try adding effects in front of the stock because right now it looks like you just plastered the image on top of the background. For the third one, take off the spray paint effect because it is a bit destracting and lighten it up a bit because it's very dark. With the Paine tag the spray paint also has to go and replace it with more lighting bursts or effects. The image of Paine itself looks a bit choppy the way it was rendered but maybe that's because of the spray paint. Both the avatars are good, I have no real complaints on those. Overall it's a good effort that you put into these, just keep practicing. :3