I think they look quite nice! It is definitely not "the usual style" which is a good thing in my opinion, but does affect what projects they could be used in.

What I mean is, the overall look is slightly messy and I mean that in the best way possible ^.^ Compare to something like this which has softer color transitions and more distinct boundaries. I do like your work though, it has a grainy naturalness to it which is cool. I point this difference out because I think the rest of the game would have to have a similar vibe in order for these sprites to fit in properly. I guess that's a consideration for all artwork and sounds kinda obvious, and really someone might come along and say "this is exactly what I'm looking for." I would consider adding some tags that might help connect to that person... words that they might search for such as "natural" or "grainy"

I do see some things that I think could be improved, mainly with the outlines and shading. For example some of the bars are not looking too hot... the red and olive green ones near the top look the best to me, while the magenta one looks the worst. Some of the pieces of wood look flat rather than round. A few of the outlines are interesting colors that I'm not sure about... I guess some of them are supposed to be glowing? I'm mainly talking about the purple rough ore that has a red outline, and some of the cubes. I would think these outlines should be darker.