Wow, been a while since I posted here. I feel kind of bad.
Anyway, when it comes to style I have to agree with helm that style is a bit of a biased concept and hard to really 'categorise'. That being said I like the idea of sharing style information with others because it gives inspiring pixel artists the chance to learn different ways of approaching things. I know I certainly learnt a lot from imitating ilkke's Cat of Gold (even though I was too noob to quite capture it). There are also a bunch of things inspiring artists simply don't even consider.
Joe for example who does mostly C64 demoscene work has a habit of putting overlaying patterns on his work:
http://www.pixeljoint.com/pixelart/68407.htmIt's something that I personally find pretty neat and not something I had ever considered doing.
Some times you just run into a style when trying to be creative:
http://www.pixeljoint.com/pixelart/67986.htm#This 'style' was design by combining African colours with a bit of a unique dithering approach. (and I was still pretty noob then)
So for me personally while defining style in it's abstract/realism/symbolism triangle is brilliant - I also feel that dither styles and colour styles are a neat thing to discuss. Colour decisions of course are important all forms of art but I find in pixelart it holds a greater impact due to the great appeal of restricted colour pallets. It's been mentioned that a lot of artist like the desaturated pallets such as the C64 pallet as it's more flexible in the sense of connecting colours together. I for one enjoy an overly saturated pallet for how it makes images 'pop':
http://i393.photobucket.com/albums/pp16/TheUnknownArtistJak/16colourpallet_zps11a8f51a.pngThen there are dither styles (something I've been toying a lot with lately rather than actually getting anything produced). There is the pretty typical checkerboard dither but then there are a whole tonne of other dither styles such as the gradient line dither, the line dither similar to my previous 'style piece I made' dither, bubble dithering etc... Often these different styles can be used for emphasising texture (line dithering on metal etc.. but they can be used just to create something unique.
On top of those couple things there are different methods to handling the borders of objects within a piece. There is outside anti-aliasing where you AA towards a surrounding colour or to a neautral middle colour. There is the broken AA where you dither AA a given colour into the outside colour (often creates a furry vibe though). There is sell-out which is shifting the outside pixels to a darker colour or good old fashion outlining; outlining itself though can be single black outlines, to bold heavy outlines to light/shade affected outlines that change in relation to the light source.
Of course none of these is a defined style but a instead different approaches that can lead to a style when combined. So yeah, as helm stated, it can't really be categorised.
I want to post more but I'm terrible at wording stuff today and honestly I aso just want to go play a tonne of my new steam games.