your links doesnt works. 

 The shading on those tubes should not be that gradient . (If that's the word.) I think that you should put some more work into them and make them your own style .

Here is 2 links on what I mean . (They are not pixelated , I just wrote them here so that you could see how steel looks in an more realistic way .)

http://www.google.se/imgres?q=pixel+art+steel+shading&hl=en&biw=1120&bih=608&tbm=isch&tbnid=1us-e4Vz3eixCM:&imgrefurl=http://www.wayofthepixel.net/index.php%3Faction%3Dprofile%3Barea%3Dshowposts%3Bu%3D8486&imgurl=http://www.traegergrills.com/images/products/bucket.jpg&w=350&h=350&ei=jBk-UMCWIM2O4gST8YHYCQ&zoom=1&iact=rc&dur=610&sig=103366251929194000072&page=4&tbnh=142&tbnw=142&start=66&ndsp=24&ved=1t:429,r:20,s:66,i:345&tx=73&ty=82

http://www.google.se/imgres?q=pixel+art+steel+shading&hl=en&biw=1120&bih=608&tbm=isch&tbnid=d0O_dKFL4IGI_M:&imgrefurl=http://ekoirasuto.deviantart.com/art/steel-glass-Shading-tutorial-272227360&imgurl=http://www.deviantart.com/download/272227360/steel_glass_shading_tutorial_by_ekoirasuto-d4i2rz4.jpg&w=1315&h=419&ei=jBk-UMCWIM2O4gST8YHYCQ&zoom=1&iact=rc&dur=264&sig=103366251929194000072&page=1&tbnh=58&tbnw=182&start=0&ndsp=18&ved=1t:429,r:10,s:0,i:100&tx=87&ty=25

PS . Sorry for my bad english .

Edit : What about now ? And if not then just search after steel shading in google or something. Improvise . :)