Looking nice.
On the first one You have too much black - that thing that looks like huge ladder in the centerline (that 1-pixel thick one, not the structural elements that are 3-pixel thick) could be in some other (dark) color to avoid creating lumps of black.
And shading doesn't seem to be symmetrical - it's "thicker" along the bottom than along the top.
Plus, it should be on 1000 x 330 px template with a caption (name of the thing in question and Your username in the upper-right and shipbucket.com watermark in the bottom-right).