Some elements on the skin don't exactly match with the sort of minimalist theme you're going for. Some of them appear too flat and some appear to stand out. Try sticking with the black and blue color scheme you're trying to use and add some light drop shadows or gradients to eliminate the "bland" sort of feel on the skin. The mania skin also looks out of place. This is only my personal preference and I think you could disagree. Honestly, it already looks nice and smooth but could use some more work.
Minimal designs can be flat. It isn't limited to the so-called "dichromatic color scheme" since that WOULD DEFINITELY SUCK for a skin with a specific theme. Leave it as is; improve some elements out there.