They dont seem to be improving from early days to present, but some of them are awesome, some of them are not that good, mix and match really, but on the whole, pretty nice.
Alot of these are just plain. No offense but if someone is looking at your work the only thing noticeable would be the render image.
for example, lets take this sig
I like the Spy render, nice and clean, but its just a black background. Sure, brushes could spruce this up, but for sigs like these I usually take an image of some scenery of whatever the render's from and put it as the sig. Since this is TF2, lets just use 2fort (A TF2 map) as scenery. I don't want to edit your work, but imagine the render with 2fort in the background. Sounds more interesting.
Or you could make your own background with a combo of smudging and C4D, like the one I made yesterday:
your very right but alot of this is personal preference. The reason I did it like that is because I like the "clean" look. I like high resolution and clean look. If you were to see that picture before you would see how much work actually went into making it the way it is. I thank you for your imput it does mean alot. I just like clean looking sigs. Look at my current sig all it is is a background the same color as this forum and a carbon fiber font with some modification.