Can ya'll stop being nice and just admit it's really not that good. Like don't sugarcoat it.
Yeah it can be harsh, but that's what criticism is about, if you wanna get good then you need to keep on practicing, study style, and try to replicate them. Learn how their shading works and such. Play with light sources.
Try and replicate this gun for example, or put your own twists on it, could even try to follow the lighting as a guide to your shading. Start with references first man, eventually you won't need them as much.
As for your lines, they look a bit jaggy, meaning they're not as smooth as you'd probably like them to be.
An example:
So in other words, use the 1-2-3 step of ordering pixels instead of 1-3-1 and such, and try to make sure everything has a shape, like I noticed the trigger guard (thing around the trigger) is a single line. It would look better if it was at least 2-3 pixels wide.
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If you wanna learn some more, check out this site.
http://pixeljoint.com/forum/forum_posts.asp?TID=11299