First off, if you only have been working for two weeks, that is pretty good. What I would suggest is to look up a bunch of tutorials and time-lapses for pixel art. There is a lot you need to learn, so tutorials will help.Links:
-www.youtube.com/user/FrankieSmileShow
-https://www.youtube.com/user/uheartbeast
-https://www.youtube.com/user/unseven
(some channels with timelapses)
-https://www.indiegogo.com/projects/pixel-logic-a-visual-pixelart-guide#/ (a good tutorial, it costs though...)
If you dont want to use tutorials, go to
http://pixeljoint.com/ and study the pixel art there.
Personal criticism:
Shield:
-use more contrast and less colors
-it looks great, I don't see the bamboo...
Ring:
-more contrast, less colors
-make a more defined light source
-put some highlights where there is a dark shade to give it a metallic look
In conclusion, it looks great, especially for 16x16. As you get better, I would start to make bigger images (i.e., go from 16x16 to 32x32). Good job