I'm surprise to see that this piece have been accepted cause mine have been refused because it was supposed to be too much "oeakaki-like". Anyway i'm glad to see that your have been accepted, you're lucky you know. Be careful, maybe the next time they won't accept a piece like this one, you know it is so... hazardous... ಠ╭╮ಠ (I experienced it...)
Anyway your piece is really nice, I really like the colors and the style =D
I think the front glass does look like oekaki, but when you zoom in you realize it's not.
Wonderful by the way!
Thanks for all comments below. Hope I will become a better in pixel art soon :)
who cares whether some people think its oekaki? its fantastic! i love the sketchy feel 
While it doesn't have much aa this is definately not oekaki. The image still was very obviously zoomed to work on. You can see that by some of the minute detail on the front shading. It's not super clean and could be refined but that doesn't really make it oekaki imo.
Although the picture is very good, the pixelling is very much on the oekaki side. Since this is your first pixel art, and you seem to have pretty good general artistic knowledge and talent I figure I should let you know these type of sketchy, oekaki drawings are not usually accepted into the gallery.
You might want to consider trying to control the pixel placements at least a bit more precisely in your latter pieces.
The palette is awesome, btw.
Damn, I love it.