Jeeze, I think that edit was on a bit higher level then I can manage, but I was kinda of going for simple.  I could try to make them a little bigger so I could put a label on them

thats quite simple dont u think?!....

make them round first, now they look like hexagons.... also add details, like rust, a label, those characteristic riffles etc.., dont use a light source coming from straight forward, place it more to the side so that  its not that symetric, which looks very unnatural... ur shading colors are very poor in contrast, and therefore theyre barely visible. the dither doesnt work here, dither should be used very rarely on this small scale, especially on plain shiny surfaces like that of metal its not well suited since it looks kinda grainy......

a lot more can be said but instead heres an edit ( note: colors are cut down from 16 to 5 (!), and still there much more details contrast and volume. less is more! thats what pixel art is about...) 

http://i992.photobucket.com/albums/af45/oooonek/cans_and_pots_and_rocks_and_pans.gif