wow that is pretty good. hehe i have a topic in the request section that looks exactly like your first one. the same size and everything. actually it looks a whole lot like mine. i like it though lol.
They are good. Altough I'll have to admit that the first ones you made are better ^^' I advise you something. You made a good amount of abstract stuff this time. When I started working with graphics I started making more 'technical' stuff. Abstraction can be tricky and balancing the colors is quite tricky to handle too, so you should work with real renders first. About the signature you made this time, the composition is good, like, it has some flow and I like the colors, just work a bit on the detail. Keep it up =)
Wow it's nice, i like the sphere. I have a hard time of doing abstract stuff, i can only do simple things XD