On the first one you just used the "Glowing Edges" filter and colorized it red... This is a pretty good attempt at a sig, but it needs improvement. For the second one, the lighting is weird and the spartan is covered up by the blue overtop, and you never want your focal to be hard to see. The font doesn't fit with the sig. Also, the depth is off because everything is blurry... you should only blur the background. Try changing fonts and reading some tutorials on lighting and using C4Ds, they can really help.
Like kratos said, the first one is just two simple effects. The second one is pretty good, could use some work, but you're definately improving. Keep up the good work.